refactor(A2): replace blender-renderer HTTP service with render-worker Celery container

- Create render-worker/ with Dockerfile (Ubuntu + cadquery + Blender via host mount)
- Add render-worker/check_version.py: verifies Blender >= 5.0.1 at startup, Exit 1 on failure
- Add render-worker/scripts/: blender_render.py, still_render.py, turntable_render.py
- Create backend/app/services/render_blender.py: direct subprocess rendering
  - convert_step_to_stl() and export_per_part_stls() using cadquery
  - render_still(): STEP → STL → PNG via Blender subprocess
  - is_blender_available(): detects BLENDER_BIN env for render-worker context
- Create backend/app/domains/rendering/tasks.py: render_still_task + render_turntable_task
- Update step_processor.py: use subprocess path when BLENDER_BIN env is set (render-worker)
- Update step_tasks.py: generate_stl_cache uses direct cadquery instead of HTTP
- Remove blender-renderer and threejs-renderer from docker-compose.yml
- Replace worker-thumbnail with render-worker (Ubuntu + cadquery + Blender mount)
- Remove Docker SDK from backend Dockerfile (was only for flamenco scaling)
- Update .env.example: BLENDER_VERSION=5.0.1 documented
- Update celery_app.py: include domains.rendering.tasks in autodiscover

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -26,3 +26,10 @@ MAX_UPLOAD_SIZE_MB=500
 # Celery worker concurrency (default: 8 parallel CAD jobs per worker container)
 # Scale horizontally with: docker compose up --scale worker=N
 CELERY_WORKER_CONCURRENCY=8
+
+# Blender (render-worker)
+# Blender >= 5.0.1 must be installed on the host at /opt/blender
+# The render-worker container mounts it read-only via volumes: - /opt/blender:/opt/blender:ro
+BLENDER_VERSION=5.0.1
+# Set to host path if Blender is not at /opt/blender:
+# BLENDER_BIN=/usr/local/blender/blender

backend/Dockerfile

@@ -8,9 +8,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     gcc \
     && rm -rf /var/lib/apt/lists/*
 
-# Docker SDK (for dynamic flamenco-worker scaling via /var/run/docker.sock)
-RUN pip install --no-cache-dir "docker>=6.1.0"
-
 # Install Python dependencies
 COPY pyproject.toml .
 RUN pip install --no-cache-dir -e .

backend/app/api/routers/admin.py

@@ -359,24 +359,20 @@ async def generate_missing_stls(
 async def renderer_status(
     admin: User = Depends(require_admin),
 ):
-    """Check health of external renderer services."""
+    """Check health of renderer services."""
-    import httpx
+    from app.services.render_blender import find_blender, is_blender_available
-    services = {
+    blender_available = is_blender_available()
-        "pillow": {"url": None, "available": True, "note": "Built-in (always available)"},
+    blender_bin = find_blender()
-        "blender": {"url": "http://blender-renderer:8100/health", "available": False, "note": ""},
+    return {
+        "pillow": {"available": True, "note": "Built-in (always available)"},
+        "blender": {
+            "available": blender_available,
+            "note": (
+                f"render-worker subprocess ({blender_bin})"
+                if blender_available
+                else "Blender not found — check render-worker container and BLENDER_BIN"
+            ),
+        },
     }
-    async with httpx.AsyncClient(timeout=3.0) as client:
-        for name, info in services.items():
-            if info["url"] is None:
-                continue
-            try:
-                resp = await client.get(info["url"])
-                if resp.status_code == 200:
-                    data = resp.json()
-                    services[name]["available"] = True
-                    services[name]["note"] = data.get("renderer", name)
-            except Exception as e:
-                services[name]["note"] = str(e)[:100]
-    return services
 
 

backend/app/domains/rendering/tasks.py

@@ -0,0 +1,251 @@
+"""Rendering domain tasks — Celery tasks for Blender-based rendering.
+
+These tasks run on the `thumbnail_rendering` queue in the render-worker
+container, which has Blender and cadquery available.
+
+Phase A2: Initial implementation replacing the blender-renderer HTTP service.
+Phase B: This module will be expanded as part of the Domain-Driven restructure.
+"""
+import logging
+from pathlib import Path
+
+from app.tasks.celery_app import celery_app
+
+logger = logging.getLogger(__name__)
+
+
+@celery_app.task(
+    bind=True,
+    name="app.domains.rendering.tasks.render_still_task",
+    queue="thumbnail_rendering",
+    max_retries=2,
+)
+def render_still_task(
+    self,
+    step_path: str,
+    output_path: str,
+    engine: str = "cycles",
+    samples: int = 256,
+    stl_quality: str = "low",
+    smooth_angle: int = 30,
+    cycles_device: str = "auto",
+    width: int = 512,
+    height: int = 512,
+    transparent_bg: bool = False,
+    template_path: str | None = None,
+    target_collection: str = "Product",
+    material_library_path: str | None = None,
+    material_map: dict | None = None,
+    part_names_ordered: list | None = None,
+    lighting_only: bool = False,
+    shadow_catcher: bool = False,
+    rotation_x: float = 0.0,
+    rotation_y: float = 0.0,
+    rotation_z: float = 0.0,
+    noise_threshold: str = "",
+    denoiser: str = "",
+    denoising_input_passes: str = "",
+    denoising_prefilter: str = "",
+    denoising_quality: str = "",
+    denoising_use_gpu: str = "",
+) -> dict:
+    """Render a STEP file to a still PNG via Blender subprocess.
+
+    Returns render metadata dict on success.
+    Retries up to 2 times on failure (30s countdown).
+    """
+    try:
+        from app.services.render_blender import render_still
+        result = render_still(
+            step_path=Path(step_path),
+            output_path=Path(output_path),
+            engine=engine,
+            samples=samples,
+            stl_quality=stl_quality,
+            smooth_angle=smooth_angle,
+            cycles_device=cycles_device,
+            width=width,
+            height=height,
+            transparent_bg=transparent_bg,
+            template_path=template_path,
+            target_collection=target_collection,
+            material_library_path=material_library_path,
+            material_map=material_map,
+            part_names_ordered=part_names_ordered,
+            lighting_only=lighting_only,
+            shadow_catcher=shadow_catcher,
+            rotation_x=rotation_x,
+            rotation_y=rotation_y,
+            rotation_z=rotation_z,
+            noise_threshold=noise_threshold,
+            denoiser=denoiser,
+            denoising_input_passes=denoising_input_passes,
+            denoising_prefilter=denoising_prefilter,
+            denoising_quality=denoising_quality,
+            denoising_use_gpu=denoising_use_gpu,
+        )
+        logger.info(
+            "render_still_task completed: %s → %s in %.1fs",
+            Path(step_path).name, Path(output_path).name,
+            result.get("total_duration_s", 0),
+        )
+        return result
+    except Exception as exc:
+        logger.error("render_still_task failed for %s: %s", step_path, exc)
+        raise self.retry(exc=exc, countdown=30)
+
+
+@celery_app.task(
+    bind=True,
+    name="app.domains.rendering.tasks.render_turntable_task",
+    queue="thumbnail_rendering",
+    max_retries=2,
+)
+def render_turntable_task(
+    self,
+    step_path: str,
+    output_dir: str,
+    output_name: str = "turntable",
+    engine: str = "cycles",
+    samples: int = 64,
+    stl_quality: str = "low",
+    smooth_angle: int = 30,
+    cycles_device: str = "auto",
+    width: int = 1920,
+    height: int = 1080,
+    frame_count: int = 120,
+    fps: int = 30,
+    turntable_degrees: float = 360.0,
+    turntable_axis: str = "world_z",
+    bg_color: str = "",
+    template_path: str | None = None,
+    target_collection: str = "Product",
+    material_library_path: str | None = None,
+    material_map: dict | None = None,
+    part_names_ordered: list | None = None,
+    lighting_only: bool = False,
+    shadow_catcher: bool = False,
+    camera_orbit: bool = True,
+    rotation_x: float = 0.0,
+    rotation_y: float = 0.0,
+    rotation_z: float = 0.0,
+) -> dict:
+    """Render a STEP file as a turntable animation (frames + FFmpeg composite).
+
+    Returns render metadata dict on success.
+    """
+    import json
+    import os
+    import shutil
+    import subprocess
+    from app.services.render_blender import (
+        find_blender, convert_step_to_stl, export_per_part_stls
+    )
+
+    blender_bin = find_blender()
+    if not blender_bin:
+        raise RuntimeError("Blender binary not found in render-worker container")
+
+    step = Path(step_path)
+    out_dir = Path(output_dir)
+    out_dir.mkdir(parents=True, exist_ok=True)
+
+    scripts_dir = Path(os.environ.get("RENDER_SCRIPTS_DIR", "/render-scripts"))
+    turntable_script = scripts_dir / "turntable_render.py"
+
+    # STL conversion
+    stl_path = step.parent / f"{step.stem}_{stl_quality}.stl"
+    if not stl_path.exists() or stl_path.stat().st_size == 0:
+        convert_step_to_stl(step, stl_path, stl_quality)
+    parts_dir = step.parent / f"{step.stem}_{stl_quality}_parts"
+    if not (parts_dir / "manifest.json").exists():
+        try:
+            export_per_part_stls(step, parts_dir, stl_quality)
+        except Exception as exc:
+            logger.warning("per-part export non-fatal: %s", exc)
+
+    # Build turntable render arguments
+    frames_dir = out_dir / "frames"
+    frames_dir.mkdir(exist_ok=True)
+
+    cmd = [
+        blender_bin, "--background",
+        "--python", str(turntable_script),
+        "--",
+        str(stl_path),
+        str(frames_dir),
+        output_name,
+        str(width), str(height),
+        engine, str(samples), str(smooth_angle), cycles_device,
+        str(frame_count), str(fps), str(turntable_degrees), turntable_axis,
+        template_path or "",
+        target_collection,
+        material_library_path or "",
+        json.dumps(material_map) if material_map else "{}",
+        json.dumps(part_names_ordered) if part_names_ordered else "[]",
+        "1" if lighting_only else "0",
+        "1" if shadow_catcher else "0",
+        "1" if camera_orbit else "0",
+        str(rotation_x), str(rotation_y), str(rotation_z),
+    ]
+
+    try:
+        result = subprocess.run(
+            cmd, capture_output=True, text=True, timeout=3600
+        )
+        if result.returncode != 0:
+            raise RuntimeError(
+                f"Blender turntable exited {result.returncode}:\n{result.stdout[-2000:]}"
+            )
+    except Exception as exc:
+        logger.error("render_turntable_task failed: %s", exc)
+        raise self.retry(exc=exc, countdown=60)
+
+    # FFmpeg composite: frames → MP4 with optional background
+    output_mp4 = out_dir / f"{output_name}.mp4"
+    ffmpeg_cmd = _build_ffmpeg_cmd(
+        frames_dir, output_mp4, fps=fps, bg_color=bg_color
+    )
+    try:
+        subprocess.run(ffmpeg_cmd, check=True, capture_output=True, text=True, timeout=300)
+    except subprocess.CalledProcessError as exc:
+        raise RuntimeError(f"FFmpeg composite failed: {exc.stderr[-500:]}")
+
+    return {
+        "output_mp4": str(output_mp4),
+        "frame_count": frame_count,
+        "fps": fps,
+    }
+
+
+def _build_ffmpeg_cmd(
+    frames_dir: Path, output_mp4: Path, fps: int = 30, bg_color: str = ""
+) -> list:
+    """Build FFmpeg command for compositing turntable frames to MP4."""
+    import shutil as _shutil
+    ffmpeg = _shutil.which("ffmpeg") or "ffmpeg"
+    frame_pattern = str(frames_dir / "%04d.png")
+
+    if bg_color:
+        # Overlay transparent frames onto solid color background
+        r = int(bg_color[1:3], 16) if bg_color.startswith("#") else 255
+        g = int(bg_color[3:5], 16) if bg_color.startswith("#") else 255
+        b = int(bg_color[5:7], 16) if bg_color.startswith("#") else 255
+        color_str = f"color=c=0x{r:02x}{g:02x}{b:02x}:s=1920x1080:r={fps}"
+        return [
+            ffmpeg, "-y",
+            "-f", "lavfi", "-i", color_str,
+            "-framerate", str(fps), "-i", frame_pattern,
+            "-filter_complex", "[0:v][1:v]overlay=0:0",
+            "-c:v", "libx264", "-pix_fmt", "yuv420p",
+            "-movflags", "+faststart",
+            str(output_mp4),
+        ]
+    else:
+        return [
+            ffmpeg, "-y",
+            "-framerate", str(fps), "-i", frame_pattern,
+            "-c:v", "libx264", "-pix_fmt", "yuv420p",
+            "-movflags", "+faststart",
+            str(output_mp4),
+        ]

backend/app/services/render_blender.py

@@ -0,0 +1,330 @@
+"""Direct Blender rendering service — runs Blender as a subprocess.
+
+Used by the render-worker Celery container (which has BLENDER_BIN set and
+cadquery installed). The backend and standard workers fall back to the Pillow
+placeholder when this service is unavailable.
+"""
+import json
+import logging
+import os
+import shutil
+import signal
+import subprocess
+from pathlib import Path
+
+logger = logging.getLogger(__name__)
+
+MIN_BLENDER_VERSION = (5, 0, 1)
+
+
+def find_blender() -> str:
+    """Locate the Blender binary via $BLENDER_BIN or PATH."""
+    env_bin = os.environ.get("BLENDER_BIN", "")
+    if env_bin and Path(env_bin).exists():
+        return env_bin
+    found = shutil.which("blender")
+    return found or ""
+
+
+def is_blender_available() -> bool:
+    """Return True if a Blender binary is reachable from this process."""
+    return bool(find_blender())
+
+
+def convert_step_to_stl(step_path: Path, stl_path: Path, quality: str = "low") -> None:
+    """Convert a STEP file to STL using cadquery.
+
+    Raises ImportError if cadquery is not installed (not available in backend
+    container — only in render-worker container).
+    """
+    import cadquery as cq  # only available in render-worker
+
+    if quality == "high":
+        shape = cq.importers.importStep(str(step_path))
+        cq.exporters.export(shape, str(stl_path), tolerance=0.01, angularTolerance=0.02)
+    else:
+        shape = cq.importers.importStep(str(step_path))
+        cq.exporters.export(shape, str(stl_path), tolerance=0.3, angularTolerance=0.3)
+
+    if not stl_path.exists() or stl_path.stat().st_size == 0:
+        raise RuntimeError("cadquery produced empty STL")
+
+
+def export_per_part_stls(step_path: Path, parts_dir: Path, quality: str = "low") -> list:
+    """Export one STL per named STEP leaf shape using OCP XCAF.
+
+    Returns the manifest list (may be empty on failure — non-fatal).
+    """
+    tol = 0.01 if quality == "high" else 0.3
+    angular_tol = 0.05 if quality == "high" else 0.3
+
+    try:
+        from OCP.STEPCAFControl import STEPCAFControl_Reader
+        from OCP.XCAFDoc import XCAFDoc_DocumentTool, XCAFDoc_ShapeTool
+        from OCP.TDataStd import TDataStd_Name
+        from OCP.TDF import TDF_Label as TDF_Label_cls, TDF_LabelSequence
+        from OCP.XCAFApp import XCAFApp_Application
+        from OCP.TDocStd import TDocStd_Document
+        from OCP.TCollection import TCollection_ExtendedString
+        from OCP.IFSelect import IFSelect_RetDone
+        import cadquery as cq
+    except ImportError as e:
+        logger.warning("per-part export skipped (import error): %s", e)
+        return []
+
+    app = XCAFApp_Application.GetApplication_s()
+    doc = TDocStd_Document(TCollection_ExtendedString("XmlOcaf"))
+    app.InitDocument(doc)
+
+    reader = STEPCAFControl_Reader()
+    reader.SetNameMode(True)
+    status = reader.ReadFile(str(step_path))
+    if status != IFSelect_RetDone:
+        logger.warning("XCAF reader failed with status %s", status)
+        return []
+
+    if not reader.Transfer(doc):
+        logger.warning("XCAF transfer failed")
+        return []
+
+    shape_tool = XCAFDoc_DocumentTool.ShapeTool_s(doc.Main())
+    name_id = TDataStd_Name.GetID_s()
+
+    leaves = []
+
+    def _get_label_name(label):
+        name_attr = TDataStd_Name()
+        if label.FindAttribute(name_id, name_attr):
+            return name_attr.Get().ToExtString()
+        return ""
+
+    def _collect_leaves(label):
+        if XCAFDoc_ShapeTool.IsAssembly_s(label):
+            components = TDF_LabelSequence()
+            XCAFDoc_ShapeTool.GetComponents_s(label, components)
+            for i in range(1, components.Length() + 1):
+                comp_label = components.Value(i)
+                if XCAFDoc_ShapeTool.IsReference_s(comp_label):
+                    ref_label = TDF_Label_cls()
+                    XCAFDoc_ShapeTool.GetReferredShape_s(comp_label, ref_label)
+                    comp_name = _get_label_name(comp_label)
+                    ref_name = _get_label_name(ref_label)
+                    name = ref_name or comp_name
+                    if XCAFDoc_ShapeTool.IsAssembly_s(ref_label):
+                        _collect_leaves(ref_label)
+                    elif XCAFDoc_ShapeTool.IsSimpleShape_s(ref_label):
+                        shape = XCAFDoc_ShapeTool.GetShape_s(comp_label)
+                        leaves.append((name or f"unnamed_{len(leaves)}", shape))
+                else:
+                    _collect_leaves(comp_label)
+        elif XCAFDoc_ShapeTool.IsSimpleShape_s(label):
+            name = _get_label_name(label)
+            shape = XCAFDoc_ShapeTool.GetShape_s(label)
+            leaves.append((name or f"unnamed_{len(leaves)}", shape))
+
+    top_labels = TDF_LabelSequence()
+    shape_tool.GetFreeShapes(top_labels)
+    for i in range(1, top_labels.Length() + 1):
+        _collect_leaves(top_labels.Value(i))
+
+    if not leaves:
+        logger.warning("no leaf shapes found via XCAF")
+        return []
+
+    parts_dir.mkdir(parents=True, exist_ok=True)
+    manifest = []
+
+    for idx, (name, shape) in enumerate(leaves):
+        safe_name = name.replace("/", "_").replace("\\", "_").replace(" ", "_")
+        filename = f"{idx:02d}_{safe_name}.stl"
+        filepath = str(parts_dir / filename)
+        try:
+            cq_shape = cq.Shape(shape)
+            cq_shape.exportStl(filepath, tolerance=tol, angularTolerance=angular_tol)
+            manifest.append({"index": idx, "name": name, "file": filename})
+        except Exception as e:
+            logger.warning("failed to export part '%s': %s", name, e)
+
+    manifest_path = parts_dir / "manifest.json"
+    with open(manifest_path, "w") as f:
+        json.dump({"parts": manifest}, f, indent=2)
+
+    return manifest
+
+
+def render_still(
+    step_path: Path,
+    output_path: Path,
+    width: int = 512,
+    height: int = 512,
+    engine: str = "cycles",
+    samples: int = 256,
+    stl_quality: str = "low",
+    smooth_angle: int = 30,
+    cycles_device: str = "auto",
+    transparent_bg: bool = False,
+    part_colors: dict | None = None,
+    template_path: str | None = None,
+    target_collection: str = "Product",
+    material_library_path: str | None = None,
+    material_map: dict | None = None,
+    part_names_ordered: list | None = None,
+    lighting_only: bool = False,
+    shadow_catcher: bool = False,
+    rotation_x: float = 0.0,
+    rotation_y: float = 0.0,
+    rotation_z: float = 0.0,
+    noise_threshold: str = "",
+    denoiser: str = "",
+    denoising_input_passes: str = "",
+    denoising_prefilter: str = "",
+    denoising_quality: str = "",
+    denoising_use_gpu: str = "",
+) -> dict:
+    """Convert STEP → STL (cadquery) → PNG (Blender subprocess).
+
+    Returns a dict with timing, sizes, engine_used, and log_lines.
+    Raises RuntimeError on failure.
+    """
+    import time
+
+    blender_bin = find_blender()
+    if not blender_bin:
+        raise RuntimeError("Blender binary not found — check BLENDER_BIN env or PATH")
+
+    script_path = Path(os.environ.get("RENDER_SCRIPTS_DIR", "/render-scripts")) / "blender_render.py"
+    if not script_path.exists():
+        # Fallback: look next to this file (development mode)
+        alt = Path(__file__).parent.parent.parent.parent / "render-worker" / "scripts" / "blender_render.py"
+        if alt.exists():
+            script_path = alt
+        else:
+            raise RuntimeError(f"blender_render.py not found at {script_path}")
+
+    t0 = time.monotonic()
+
+    # 1. STL conversion (cadquery)
+    stl_path = step_path.parent / f"{step_path.stem}_{stl_quality}.stl"
+    parts_dir = step_path.parent / f"{step_path.stem}_{stl_quality}_parts"
+
+    t_stl = time.monotonic()
+    if not stl_path.exists() or stl_path.stat().st_size == 0:
+        logger.info("STL cache miss — converting: %s", step_path.name)
+        convert_step_to_stl(step_path, stl_path, stl_quality)
+    else:
+        logger.info("STL cache hit: %s (%d KB)", stl_path.name, stl_path.stat().st_size // 1024)
+    stl_size_bytes = stl_path.stat().st_size if stl_path.exists() else 0
+
+    if not (parts_dir / "manifest.json").exists():
+        try:
+            export_per_part_stls(step_path, parts_dir, stl_quality)
+        except Exception as exc:
+            logger.warning("per-part STL export failed (non-fatal): %s", exc)
+
+    stl_duration_s = round(time.monotonic() - t_stl, 2)
+
+    # 2. Blender render
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+
+    env = dict(os.environ)
+    if engine == "eevee":
+        env.update({
+            "VK_ICD_FILENAMES":         "/usr/share/vulkan/icd.d/lvp_icd.x86_64.json",
+            "LIBGL_ALWAYS_SOFTWARE":    "1",
+            "MESA_GL_VERSION_OVERRIDE": "4.5",
+            "EGL_PLATFORM":             "surfaceless",
+        })
+    else:
+        env["EGL_PLATFORM"] = "surfaceless"
+
+    def _build_cmd(eng: str) -> list:
+        return [
+            blender_bin,
+            "--background",
+            "--python", str(script_path),
+            "--",
+            str(stl_path),
+            str(output_path),
+            str(width), str(height),
+            eng, str(samples), str(smooth_angle),
+            cycles_device,
+            "1" if transparent_bg else "0",
+            template_path or "",
+            target_collection,
+            material_library_path or "",
+            json.dumps(material_map) if material_map else "{}",
+            json.dumps(part_names_ordered) if part_names_ordered else "[]",
+            "1" if lighting_only else "0",
+            "1" if shadow_catcher else "0",
+            str(rotation_x), str(rotation_y), str(rotation_z),
+            noise_threshold or "", denoiser or "",
+            denoising_input_passes or "", denoising_prefilter or "",
+            denoising_quality or "", denoising_use_gpu or "",
+        ]
+
+    def _run(eng: str) -> subprocess.CompletedProcess:
+        proc = subprocess.Popen(
+            _build_cmd(eng),
+            stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+            text=True, env=env, start_new_session=True,
+        )
+        try:
+            stdout, stderr = proc.communicate(timeout=600)
+        except subprocess.TimeoutExpired:
+            try:
+                os.killpg(os.getpgid(proc.pid), signal.SIGTERM)
+            except (ProcessLookupError, OSError):
+                pass
+            stdout, stderr = proc.communicate()
+        return subprocess.CompletedProcess(_build_cmd(eng), proc.returncode, stdout, stderr)
+
+    t_render = time.monotonic()
+    result = _run(engine)
+    engine_used = engine
+
+    log_lines = []
+    for line in (result.stdout or "").splitlines():
+        logger.info("[blender] %s", line)
+        if "[blender_render]" in line:
+            log_lines.append(line)
+    for line in (result.stderr or "").splitlines():
+        logger.warning("[blender stderr] %s", line)
+
+    # EEVEE fallback to Cycles on non-signal error
+    if result.returncode > 0 and engine == "eevee":
+        logger.warning("EEVEE failed (exit %d) — retrying with Cycles", result.returncode)
+        result = _run("cycles")
+        engine_used = "cycles (eevee fallback)"
+        for line in (result.stdout or "").splitlines():
+            logger.info("[blender-fallback] %s", line)
+            if "[blender_render]" in line:
+                log_lines.append(line)
+
+    if result.returncode != 0:
+        raise RuntimeError(
+            f"Blender exited with code {result.returncode}.\n"
+            f"stdout: {(result.stdout or '')[-2000:]}\n"
+            f"stderr: {(result.stderr or '')[-500:]}"
+        )
+
+    render_duration_s = round(time.monotonic() - t_render, 2)
+
+    parts_count = 0
+    manifest_file = parts_dir / "manifest.json"
+    if manifest_file.exists():
+        try:
+            data = json.loads(manifest_file.read_text())
+            parts_count = len(data.get("parts", []))
+        except Exception:
+            pass
+
+    return {
+        "total_duration_s": round(time.monotonic() - t0, 2),
+        "stl_duration_s": stl_duration_s,
+        "render_duration_s": render_duration_s,
+        "stl_size_bytes": stl_size_bytes,
+        "output_size_bytes": output_path.stat().st_size if output_path.exists() else 0,
+        "parts_count": parts_count,
+        "engine_used": engine_used,
+        "log_lines": log_lines,
+    }

backend/app/services/step_processor.py

@@ -329,8 +329,9 @@ def _generate_thumbnail(
             "height": 512,
         })
     elif renderer == "threejs":
-        size = int(settings["threejs_render_size"])
+        # Three.js renderer removed in v2; treat as pillow fallback
-        render_log.update({"width": size, "height": size})
+        renderer = "pillow"
+        render_log.update({"renderer": "pillow", "threejs_removed": True})
 
     logger.info(f"Thumbnail renderer={renderer}, format={fmt}")
 
@@ -340,29 +341,25 @@ def _generate_thumbnail(
     if renderer == "blender":
         engine  = settings["blender_engine"]
         samples = int(settings[f"blender_{engine}_samples"])
-        extra   = {
-            "engine": engine,
-            "samples": samples,
-            "stl_quality": settings["stl_quality"],
-            "smooth_angle": int(settings["blender_smooth_angle"]),
-            "cycles_device": settings["cycles_device"],
-        }
-        rendered_png, service_data = _render_via_service(
-            "http://blender-renderer:8100/render", step_path, tmp_png, extra
-        )
-        if not rendered_png:
-            logger.warning("Blender renderer failed; falling back to Pillow placeholder")
 
-    elif renderer == "threejs":
+        from app.services.render_blender import is_blender_available, render_still
-        size = int(settings["threejs_render_size"])
+        if is_blender_available():
-        extra2: dict = {"width": size, "height": size}
+            try:
-        if part_colors is not None:
+                service_data = render_still(
-            extra2["part_colors"] = part_colors
+                    step_path=step_path,
-        rendered_png, service_data = _render_via_service(
+                    output_path=tmp_png,
-            "http://threejs-renderer:8101/render", step_path, tmp_png, extra2
+                    engine=engine,
-        )
+                    samples=samples,
-        if not rendered_png:
+                    stl_quality=settings["stl_quality"],
-            logger.warning("Three.js renderer failed; falling back to Pillow placeholder")
+                    smooth_angle=int(settings["blender_smooth_angle"]),
+                    cycles_device=settings["cycles_device"],
+                )
+                rendered_png = tmp_png if tmp_png.exists() else None
+            except Exception as exc:
+                logger.warning("Blender subprocess render failed: %s", exc)
+                rendered_png = None
+        else:
+            logger.warning("Blender not available in this container — falling back to Pillow placeholder")
 
     # Merge rich service response data into render_log
     if service_data:
@@ -669,20 +666,43 @@ def render_to_file(
             extra["denoising_quality"] = denoising_quality
         if denoising_use_gpu:
             extra["denoising_use_gpu"] = denoising_use_gpu
-        rendered_png, service_data = _render_via_service(
+        from app.services.render_blender import is_blender_available, render_still
-            "http://blender-renderer:8100/render", step, tmp_png, extra, job_id=job_id
+        if is_blender_available():
-        )
+            try:
+                service_data = render_still(
+                    step_path=step,
+                    output_path=tmp_png,
+                    engine=actual_engine,
+                    samples=actual_samples,
+                    stl_quality=settings["stl_quality"],
+                    smooth_angle=int(settings["blender_smooth_angle"]),
+                    cycles_device=actual_cycles_device,
+                    width=w, height=h,
+                    transparent_bg=transparent_bg,
+                    part_colors=part_colors,
+                    template_path=template_path,
+                    target_collection=target_collection,
+                    material_library_path=material_library_path,
+                    material_map=material_map,
+                    part_names_ordered=part_names_ordered,
+                    lighting_only=lighting_only,
+                    shadow_catcher=shadow_catcher,
+                    rotation_x=rotation_x, rotation_y=rotation_y, rotation_z=rotation_z,
+                    noise_threshold=noise_threshold, denoiser=denoiser,
+                    denoising_input_passes=denoising_input_passes,
+                    denoising_prefilter=denoising_prefilter,
+                    denoising_quality=denoising_quality,
+                    denoising_use_gpu=denoising_use_gpu,
+                )
+                rendered_png = tmp_png if tmp_png.exists() else None
+            except Exception as exc:
+                logger.warning("Blender subprocess render failed: %s", exc)
+                rendered_png = None
+        else:
+            logger.warning("Blender not available in this container — using Pillow fallback")
     elif renderer == "threejs":
-        default_size = int(settings["threejs_render_size"])
+        # Three.js renderer removed in v2 — fall through to Pillow placeholder
-        w = width or default_size
+        logger.warning("Three.js renderer removed; using Pillow fallback")
-        h = height or default_size
-        render_log.update({"width": w, "height": h})
-        extra2: dict = {"width": w, "height": h}
-        if part_colors is not None:
-            extra2["part_colors"] = part_colors
-        rendered_png, service_data = _render_via_service(
-            "http://threejs-renderer:8101/render", step, tmp_png, extra2
-        )
 
     if service_data:
         for key in ("total_duration_s", "stl_duration_s", "render_duration_s",

backend/app/tasks/celery_app.py

@@ -5,7 +5,11 @@ celery_app = Celery(
     "schaefflerautomat",
     broker=settings.redis_url,
     backend=settings.redis_url,
-    include=["app.tasks.step_tasks", "app.tasks.ai_tasks"],
+    include=[
+        "app.tasks.step_tasks",
+        "app.tasks.ai_tasks",
+        "app.domains.rendering.tasks",
+    ],
 )
 
 celery_app.conf.update(
@@ -17,6 +21,7 @@ celery_app.conf.update(
     task_routes={
         "app.tasks.step_tasks.*": {"queue": "step_processing"},
         "app.tasks.ai_tasks.*": {"queue": "ai_validation"},
+        "app.domains.rendering.tasks.*": {"queue": "thumbnail_rendering"},
     },
     beat_schedule={},
 )

backend/app/tasks/step_tasks.py

@@ -157,7 +157,6 @@ def generate_stl_cache(self, cad_file_id: str, quality: str):
     from sqlalchemy.orm import Session
     from app.config import settings as app_settings
     from app.models.cad_file import CadFile
-    import httpx
 
     logger.info(f"Generating {quality}-quality STL for CAD file: {cad_file_id}")
 
@@ -172,16 +171,20 @@ def generate_stl_cache(self, cad_file_id: str, quality: str):
     eng.dispose()
 
     try:
-        resp = httpx.post(
+        from app.services.render_blender import convert_step_to_stl, export_per_part_stls
-            "http://blender-renderer:8100/convert-stl",
+        from pathlib import Path as _Path
-            json={"step_path": step_path, "quality": quality},
+        step = _Path(step_path)
-            timeout=600.0,
+        stl_out = step.parent / f"{step.stem}_{quality}.stl"
-        )
+        parts_dir = step.parent / f"{step.stem}_{quality}_parts"
-        if resp.status_code == 200:
+
-            data = resp.json()
+        if not stl_out.exists() or stl_out.stat().st_size == 0:
-            logger.info(f"STL cached: {data['stl_path']} ({data['size_bytes']} bytes) in {data['duration_s']}s")
+            convert_step_to_stl(step, stl_out, quality)
-        else:
+        if not (parts_dir / "manifest.json").exists():
-            raise RuntimeError(f"blender-renderer returned {resp.status_code}: {resp.text[:300]}")
+            try:
+                export_per_part_stls(step, parts_dir, quality)
+            except Exception as pe:
+                logger.warning(f"Per-part STL export non-fatal: {pe}")
+        logger.info(f"STL cached: {stl_out} ({stl_out.stat().st_size // 1024} KB)")
     except Exception as exc:
         logger.error(f"STL generation failed for {cad_file_id} quality={quality}: {exc}")
         raise self.retry(exc=exc, countdown=30, max_retries=2)

docker-compose.yml

@@ -49,7 +49,6 @@ services:
     volumes:
       - ./backend:/app
       - uploads:/app/uploads
-      - /var/run/docker.sock:/var/run/docker.sock
     ports:
       - "8888:8888"
     depends_on:
@@ -86,11 +85,12 @@ services:
       redis:
         condition: service_healthy
 
-  worker-thumbnail:
+  render-worker:
     build:
-      context: ./backend
+      context: ./render-worker
       dockerfile: Dockerfile
-    command: celery -A app.tasks.celery_app worker --loglevel=info -Q thumbnail_rendering --concurrency=1
+      args:
+        - BLENDER_VERSION=${BLENDER_VERSION:-5.0.1}
     environment:
       - POSTGRES_DB=${POSTGRES_DB:-schaeffler}
       - POSTGRES_USER=${POSTGRES_USER:-schaeffler}
@@ -99,19 +99,25 @@ services:
       - POSTGRES_PORT=5432
       - REDIS_URL=${REDIS_URL:-redis://redis:6379/0}
       - JWT_SECRET_KEY=${JWT_SECRET_KEY:-changeme-in-production}
-      - AZURE_OPENAI_API_KEY=${AZURE_OPENAI_API_KEY:-}
-      - AZURE_OPENAI_ENDPOINT=${AZURE_OPENAI_ENDPOINT:-}
-      - AZURE_OPENAI_DEPLOYMENT=${AZURE_OPENAI_DEPLOYMENT:-gpt-4o}
-      - AZURE_OPENAI_API_VERSION=${AZURE_OPENAI_API_VERSION:-2024-02-01}
       - UPLOAD_DIR=/app/uploads
+      - BLENDER_BIN=/opt/blender/blender
+      - RENDER_SCRIPTS_DIR=/render-scripts
     volumes:
       - ./backend:/app
       - uploads:/app/uploads
+      - /opt/blender:/opt/blender:ro
     depends_on:
       postgres:
         condition: service_healthy
       redis:
         condition: service_healthy
+    deploy:
+      resources:
+        reservations:
+          devices:
+            - driver: nvidia
+              count: 1
+              capabilities: [gpu, compute, utility, graphics]
 
   beat:
     build:
@@ -140,36 +146,6 @@ services:
       redis:
         condition: service_healthy
 
-  blender-renderer:
-    build:
-      context: ./blender-renderer
-      dockerfile: Dockerfile
-    ports:
-      - "8100:8100"
-    volumes:
-      - uploads:/app/uploads
-      - ./blender-renderer:/app
-      - /opt/blender:/opt/blender:ro
-    restart: unless-stopped
-    deploy:
-      resources:
-        reservations:
-          devices:
-            - driver: nvidia
-              count: 1
-              capabilities: [gpu, compute, utility, graphics]
-
-  threejs-renderer:
-    build:
-      context: ./threejs-renderer
-      dockerfile: Dockerfile
-    ports:
-      - "8101:8101"
-    volumes:
-      - uploads:/app/uploads
-      - ./threejs-renderer:/app
-    restart: unless-stopped
-
   frontend:
     build:
       context: ./frontend

render-worker/Dockerfile

@@ -0,0 +1,61 @@
+FROM ubuntu:22.04
+
+ARG BLENDER_VERSION=5.0.1
+ENV DEBIAN_FRONTEND=noninteractive
+ENV PYTHONUNBUFFERED=1
+ENV BLENDER_VERSION=${BLENDER_VERSION}
+# Blender 5.x is mounted from the host at /opt/blender (see docker-compose.yml)
+ENV BLENDER_BIN=/opt/blender/blender
+# OSMesa for headless cadquery/VTK (no display needed)
+ENV PYOPENGL_PLATFORM=osmesa
+ENV VTK_DEFAULT_EGL=0
+
+# Runtime libraries for cadquery/OCC + Blender 5.x headless
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    python3-pip \
+    python3-dev \
+    libpq-dev \
+    gcc \
+    libxrender1 \
+    libxi6 \
+    libxkbcommon-x11-0 \
+    libsm6 \
+    libglib2.0-0 \
+    libgl1-mesa-glx \
+    libosmesa6 \
+    libgomp1 \
+    libxfixes3 \
+    libxrandr2 \
+    libxcursor1 \
+    libxinerama1 \
+    libwayland-client0 \
+    libwayland-cursor0 \
+    libwayland-egl1 \
+    libvulkan1 \
+    mesa-vulkan-drivers \
+    libegl1 \
+    libegl-mesa0 \
+    libgbm1 \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+# Install backend Python dependencies (includes celery, sqlalchemy, fastapi, etc.)
+COPY pyproject.toml .
+RUN pip3 install --no-cache-dir -e .
+
+# Install cadquery (heavy — installed after backend deps for better layer caching)
+RUN pip3 install --no-cache-dir "cadquery>=2.4.0"
+
+# Copy render scripts
+COPY scripts/ /render-scripts/
+
+# Version check script — fails fast if Blender < 5.0.1
+COPY check_version.py /check_version.py
+
+# Copy app code (overridden by volume mount in docker-compose)
+COPY . .
+
+# Verify Blender version at build time if binary is available
+# (skipped during build since /opt/blender is a host mount)
+CMD ["bash", "-c", "python3 /check_version.py && celery -A app.tasks.celery_app worker --loglevel=info -Q thumbnail_rendering --concurrency=1"]

render-worker/check_version.py

@@ -0,0 +1,68 @@
+"""Startup check: verify Blender >= 5.0.1 is available.
+
+Run before starting the Celery worker. Exits with code 1 if Blender is
+missing or below the minimum required version.
+"""
+import os
+import re
+import subprocess
+import sys
+from pathlib import Path
+
+MIN_VERSION = (5, 0, 1)
+MIN_VERSION_STR = ".".join(str(v) for v in MIN_VERSION)
+
+
+def find_blender() -> str:
+    import shutil
+    env_bin = os.environ.get("BLENDER_BIN", "")
+    if env_bin and Path(env_bin).exists():
+        return env_bin
+    found = shutil.which("blender")
+    return found or "blender"
+
+
+def check_version():
+    blender_bin = find_blender()
+
+    if not Path(blender_bin).exists():
+        print(f"ERROR: Blender not found at {blender_bin}", file=sys.stderr)
+        print(
+            "Mount Blender >= 5.0.1 from the host via:\n"
+            "  volumes:\n"
+            "    - /opt/blender:/opt/blender:ro",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+    try:
+        result = subprocess.run(
+            [blender_bin, "--version"],
+            capture_output=True, text=True, timeout=15
+        )
+        output = result.stdout or result.stderr or ""
+    except Exception as exc:
+        print(f"ERROR: Could not run Blender: {exc}", file=sys.stderr)
+        sys.exit(1)
+
+    match = re.search(r"Blender\s+(\d+)\.(\d+)\.(\d+)", output)
+    if not match:
+        print(f"ERROR: Could not parse Blender version from output:\n{output[:200]}", file=sys.stderr)
+        sys.exit(1)
+
+    version = tuple(int(x) for x in match.groups())
+    version_str = ".".join(str(v) for v in version)
+
+    if version < MIN_VERSION:
+        print(
+            f"ERROR: Blender {version_str} < required {MIN_VERSION_STR}.\n"
+            f"Update your host Blender installation.",
+            file=sys.stderr,
+        )
+        sys.exit(1)
+
+    print(f"Blender {version_str} OK (>= {MIN_VERSION_STR})")
+
+
+if __name__ == "__main__":
+    check_version()

render-worker/scripts/blender_render.py

@@ -0,0 +1,753 @@
+"""
+Blender Python script for rendering an STL file to PNG.
+Targets Blender 5.0+ (EEVEE / Cycles).
+
+Called by Blender:
+  blender --background --python blender_render.py -- \
+      <stl_path> <output_path> <width> <height> [engine] [samples]
+
+engine: "cycles" (default) | "eevee"
+
+Features:
+- Disconnected mesh islands split into separate objects and painted with
+  palette colours (same 10-colour palette as the Three.js renderer).
+- Bounding-box-aware camera: object fills ~85 % of the frame.
+- Isometric-style angle (elevation 28°, azimuth 40°).
+- Dynamic clip planes.
+- Standard (non-Filmic) colour management → no grey tint.
+- Schaeffler green top bar + model name label via Pillow post-processing.
+"""
+import sys
+import os
+import math
+import bpy
+from mathutils import Vector, Matrix
+
+# ── Colour palette (matches Three.js renderer) ───────────────────────────────
+
+PALETTE_HEX = [
+    "#4C9BE8", "#E85B4C", "#4CBE72", "#E8A84C", "#A04CE8",
+    "#4CD4E8", "#E84CA8", "#7EC850", "#E86B30", "#5088C8",
+]
+
+def _srgb_to_linear(c: int) -> float:
+    """Convert 0-255 sRGB integer to linear float."""
+    v = c / 255.0
+    return v / 12.92 if v <= 0.04045 else ((v + 0.055) / 1.055) ** 2.4
+
+def _hex_to_linear(hex_color: str) -> tuple:
+    """Return (r, g, b, 1.0) in Blender linear colour space."""
+    h = hex_color.lstrip('#')
+    return (
+        _srgb_to_linear(int(h[0:2], 16)),
+        _srgb_to_linear(int(h[2:4], 16)),
+        _srgb_to_linear(int(h[4:6], 16)),
+        1.0,
+    )
+
+PALETTE_LINEAR = [_hex_to_linear(h) for h in PALETTE_HEX]
+
+# ── Parse arguments ───────────────────────────────────────────────────────────
+
+argv = sys.argv
+if "--" in argv:
+    argv = argv[argv.index("--") + 1:]
+else:
+    argv = []
+
+if len(argv) < 4:
+    print("Usage: blender --background --python blender_render.py -- "
+          "<stl_path> <output_path> <width> <height> [engine] [samples] [smooth_angle] [cycles_device] [transparent_bg]")
+    sys.exit(1)
+
+import json as _json
+
+stl_path    = argv[0]
+output_path = argv[1]
+width       = int(argv[2])
+height      = int(argv[3])
+engine        = argv[4].lower() if len(argv) > 4 else "cycles"
+samples       = int(argv[5])    if len(argv) > 5 else (64 if engine == "eevee" else 256)
+smooth_angle  = int(argv[6])    if len(argv) > 6 else 30   # degrees; 0 = flat shading
+cycles_device = argv[7].lower() if len(argv) > 7 else "auto"  # "auto", "gpu", "cpu"
+transparent_bg = argv[8] == "1" if len(argv) > 8 else False
+template_path  = argv[9]  if len(argv) > 9  and argv[9]  else ""
+target_collection = argv[10] if len(argv) > 10 else "Product"
+material_library_path = argv[11] if len(argv) > 11 and argv[11] else ""
+material_map_raw = argv[12] if len(argv) > 12 else "{}"
+try:
+    material_map = _json.loads(material_map_raw) if material_map_raw else {}
+except _json.JSONDecodeError:
+    material_map = {}
+
+part_names_ordered_raw = argv[13] if len(argv) > 13 else "[]"
+try:
+    part_names_ordered = _json.loads(part_names_ordered_raw) if part_names_ordered_raw else []
+except _json.JSONDecodeError:
+    part_names_ordered = []
+
+lighting_only = argv[14] == "1" if len(argv) > 14 else False
+shadow_catcher = argv[15] == "1" if len(argv) > 15 else False
+rotation_x = float(argv[16]) if len(argv) > 16 else 0.0
+rotation_y = float(argv[17]) if len(argv) > 17 else 0.0
+rotation_z = float(argv[18]) if len(argv) > 18 else 0.0
+noise_threshold_arg = argv[19] if len(argv) > 19 else ""
+denoiser_arg = argv[20] if len(argv) > 20 else ""
+denoising_input_passes_arg = argv[21] if len(argv) > 21 else ""
+denoising_prefilter_arg = argv[22] if len(argv) > 22 else ""
+denoising_quality_arg = argv[23] if len(argv) > 23 else ""
+denoising_use_gpu_arg = argv[24] if len(argv) > 24 else ""
+
+# Validate template path: if provided it MUST exist on disk.
+# Fail loudly rather than silently rendering with factory settings.
+if template_path and not os.path.isfile(template_path):
+    print(f"[blender_render] ERROR: template_path was provided but file not found: {template_path}")
+    print("[blender_render] Check that the blend-templates directory is on the shared volume.")
+    sys.exit(1)
+
+use_template = bool(template_path)
+
+print(f"[blender_render] engine={engine}, samples={samples}, size={width}x{height}, smooth_angle={smooth_angle}°, device={cycles_device}, transparent={transparent_bg}")
+print(f"[blender_render] part_names_ordered: {len(part_names_ordered)} entries")
+if use_template:
+    print(f"[blender_render] template={template_path}, collection={target_collection}, lighting_only={lighting_only}")
+else:
+    print("[blender_render] no template — using factory settings (Mode A)")
+if material_library_path:
+    print(f"[blender_render] material_library={material_library_path}, material_map keys={list(material_map.keys())}")
+
+# ── Helper: find or create collection by name ────────────────────────────────
+
+def _ensure_collection(name: str):
+    """Return a collection by name, creating it if needed."""
+    if name in bpy.data.collections:
+        return bpy.data.collections[name]
+    col = bpy.data.collections.new(name)
+    bpy.context.scene.collection.children.link(col)
+    return col
+
+
+def _apply_smooth(part_obj, angle_deg):
+    """Apply smooth or flat shading to a mesh object."""
+    bpy.context.view_layer.objects.active = part_obj
+    part_obj.select_set(True)
+    if angle_deg > 0:
+        try:
+            bpy.ops.object.shade_smooth_by_angle(angle=math.radians(angle_deg))
+        except AttributeError:
+            bpy.ops.object.shade_smooth()
+            part_obj.data.use_auto_smooth = True
+            part_obj.data.auto_smooth_angle = math.radians(angle_deg)
+    else:
+        bpy.ops.object.shade_flat()
+
+
+def _assign_palette_material(part_obj, index):
+    """Assign a palette colour material to a mesh part."""
+    color = PALETTE_LINEAR[index % len(PALETTE_LINEAR)]
+    mat = bpy.data.materials.new(name=f"Part_{index}")
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes.get("Principled BSDF")
+    if bsdf:
+        bsdf.inputs["Base Color"].default_value = color
+        bsdf.inputs["Metallic"].default_value   = 0.35
+        bsdf.inputs["Roughness"].default_value  = 0.40
+        try:
+            bsdf.inputs["Specular IOR Level"].default_value = 0.5
+        except KeyError:
+            pass
+    part_obj.data.materials.clear()
+    part_obj.data.materials.append(mat)
+
+
+import re as _re
+
+
+def _scale_mm_to_m(parts):
+    """Scale imported STL objects from mm to Blender metres (×0.001).
+
+    STEP/STL coordinates are in mm; Blender's default unit is metres.
+    Without scaling a 50 mm part appears as 50 m inside Blender — way too large
+    relative to any template environment designed in metric units.
+    """
+    if not parts:
+        return
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.scale = (0.001, 0.001, 0.001)
+        p.location *= 0.001
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(scale=True, location=False, rotation=False)
+    print(f"[blender_render] scaled {len(parts)} parts mm→m (×0.001)")
+
+
+def _apply_rotation(parts, rx, ry, rz):
+    """Apply Euler rotation (degrees, XYZ order) to all parts around world origin.
+
+    After _import_stl + _scale_mm_to_m the combined bbox center is at world origin,
+    so rotating around origin is equivalent to rotating around the assembly center.
+    """
+    if not parts or (rx == 0.0 and ry == 0.0 and rz == 0.0):
+        return
+    from mathutils import Euler
+    rot_mat = Euler((math.radians(rx), math.radians(ry), math.radians(rz)), 'XYZ').to_matrix().to_4x4()
+    for p in parts:
+        p.matrix_world = rot_mat @ p.matrix_world
+    # Bake rotation into mesh data so camera bbox calculations see the rotated geometry
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(location=False, rotation=True, scale=False)
+    print(f"[blender_render] applied rotation ({rx}°, {ry}°, {rz}°) to {len(parts)} parts")
+
+
+def _import_stl(stl_file):
+    """Import STL into Blender, using per-part STLs if available.
+
+    Checks for {stl_stem}_parts/manifest.json next to the STL file.
+    - Per-part mode: imports each part STL, names Blender object after STEP part name.
+    - Fallback: imports combined STL and splits by loose geometry.
+
+    Returns list of Blender mesh objects, centred at origin.
+    """
+    stl_dir = os.path.dirname(stl_file)
+    stl_stem = os.path.splitext(os.path.basename(stl_file))[0]
+    parts_dir = os.path.join(stl_dir, stl_stem + "_parts")
+    manifest_path = os.path.join(parts_dir, "manifest.json")
+
+    parts = []
+
+    if os.path.isfile(manifest_path):
+        # ── Per-part mode ────────────────────────────────────────────────
+        try:
+            with open(manifest_path, "r") as f:
+                manifest = _json.loads(f.read())
+            part_entries = manifest.get("parts", [])
+        except Exception as e:
+            print(f"[blender_render] WARNING: failed to read manifest: {e}")
+            part_entries = []
+
+        if part_entries:
+            for entry in part_entries:
+                part_file = os.path.join(parts_dir, entry["file"])
+                part_name = entry["name"]
+                if not os.path.isfile(part_file):
+                    print(f"[blender_render] WARNING: part STL missing: {part_file}")
+                    continue
+
+                bpy.ops.object.select_all(action='DESELECT')
+                bpy.ops.wm.stl_import(filepath=part_file)
+                imported = bpy.context.selected_objects
+                if imported:
+                    obj = imported[0]
+                    obj.name = part_name
+                    if obj.data:
+                        obj.data.name = part_name
+                    parts.append(obj)
+
+            if parts:
+                print(f"[blender_render] imported {len(parts)} named parts from per-part STLs")
+
+    # ── Fallback: combined STL + separate by loose ───────────────────────
+    if not parts:
+        bpy.ops.wm.stl_import(filepath=stl_file)
+        obj = bpy.context.selected_objects[0] if bpy.context.selected_objects else None
+        if obj is None:
+            print(f"ERROR: No objects imported from {stl_file}")
+            sys.exit(1)
+
+        bpy.context.view_layer.objects.active = obj
+        bpy.ops.object.origin_set(type='ORIGIN_GEOMETRY', center='BOUNDS')
+        obj.location = (0.0, 0.0, 0.0)
+
+        bpy.ops.object.mode_set(mode='EDIT')
+        bpy.ops.mesh.separate(type='LOOSE')
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        parts = list(bpy.context.selected_objects)
+        print(f"[blender_render] fallback: separated into {len(parts)} part(s)")
+        return parts
+
+    # ── Centre per-part imports at origin (combined bbox) ────────────────
+    all_corners = []
+    for p in parts:
+        all_corners.extend(p.matrix_world @ Vector(c) for c in p.bound_box)
+
+    if all_corners:
+        mins = Vector((min(v.x for v in all_corners),
+                        min(v.y for v in all_corners),
+                        min(v.z for v in all_corners)))
+        maxs = Vector((max(v.x for v in all_corners),
+                        max(v.y for v in all_corners),
+                        max(v.z for v in all_corners)))
+        center = (mins + maxs) * 0.5
+        for p in parts:
+            p.location -= center
+
+    return parts
+
+
+def _resolve_part_name(index, part_obj):
+    """Get the STEP part name for a Blender part by index.
+
+    With per-part import, part_obj.name IS the STEP name (possibly with
+    Blender .NNN suffix for duplicates). Strip that suffix for lookup.
+    Falls back to part_names_ordered index mapping for combined-STL mode.
+    """
+    # Strip Blender auto-suffix (.001, .002, etc.)
+    base_name = _re.sub(r'\.\d{3}$', '', part_obj.name)
+    # If the base name looks like a real STEP part name (not generic "Cube" etc.),
+    # use it directly
+    if part_names_ordered and index < len(part_names_ordered):
+        return part_names_ordered[index]
+    return base_name
+
+
+def _apply_material_library(parts, mat_lib_path, mat_map):
+    """Append materials from library .blend and assign to parts via material_map.
+
+    With per-part STL import, Blender objects are named after STEP parts,
+    so matching is by name (stripping Blender .NNN suffix for duplicates).
+    Falls back to part_names_ordered index-based matching for combined-STL mode.
+
+    mat_map: {part_name_lower: material_name}
+    Parts without a match keep their current material.
+    """
+    if not mat_lib_path or not os.path.isfile(mat_lib_path):
+        print(f"[blender_render] material library not found: {mat_lib_path}")
+        return
+
+    # Collect unique material names needed
+    needed = set(mat_map.values())
+    if not needed:
+        return
+
+    # Append materials from library
+    appended = {}
+    for mat_name in needed:
+        inner_path = f"{mat_lib_path}/Material/{mat_name}"
+        try:
+            bpy.ops.wm.append(
+                filepath=inner_path,
+                directory=f"{mat_lib_path}/Material/",
+                filename=mat_name,
+                link=False,
+            )
+            if mat_name in bpy.data.materials:
+                appended[mat_name] = bpy.data.materials[mat_name]
+                print(f"[blender_render] appended material: {mat_name}")
+            else:
+                print(f"[blender_render] WARNING: material '{mat_name}' not found after append")
+        except Exception as exc:
+            print(f"[blender_render] WARNING: failed to append material '{mat_name}': {exc}")
+
+    if not appended:
+        return
+
+    # Assign materials to parts — primary: name-based (per-part STL mode),
+    # secondary: index-based via part_names_ordered (combined STL fallback)
+    assigned_count = 0
+    for i, part in enumerate(parts):
+        # Try name-based matching first (strip Blender .NNN suffix)
+        base_name = _re.sub(r'\.\d{3}$', '', part.name)
+        part_key = base_name.lower().strip()
+        mat_name = mat_map.get(part_key)
+
+        # Fall back to index-based matching via part_names_ordered
+        if not mat_name and part_names_ordered and i < len(part_names_ordered):
+            step_name = part_names_ordered[i]
+            part_key = step_name.lower().strip()
+            mat_name = mat_map.get(part_key)
+
+        if mat_name and mat_name in appended:
+            part.data.materials.clear()
+            part.data.materials.append(appended[mat_name])
+            assigned_count += 1
+            print(f"[blender_render] assigned '{mat_name}' to part '{part.name}'")
+
+    print(f"[blender_render] material assignment: {assigned_count}/{len(parts)} parts matched")
+
+
+# ── SCENE SETUP ──────────────────────────────────────────────────────────────
+
+if use_template:
+    # ── MODE B: Template-based render ────────────────────────────────────────
+    print(f"[blender_render] Opening template: {template_path}")
+    bpy.ops.wm.open_mainfile(filepath=template_path)
+
+    # Find or create target collection
+    target_col = _ensure_collection(target_collection)
+
+    # Import and split STL
+    parts = _import_stl(stl_path)
+    # Scale mm→m: STEP coords are mm, Blender default unit is metres
+    _scale_mm_to_m(parts)
+    # Apply render position rotation (before camera/bbox calculations)
+    _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+    # Move imported parts into target collection
+    for part in parts:
+        # Remove from all existing collections
+        for col in list(part.users_collection):
+            col.objects.unlink(part)
+        target_col.objects.link(part)
+
+    # Apply smooth shading
+    for part in parts:
+        _apply_smooth(part, smooth_angle)
+
+    # Material assignment: library materials if available, otherwise palette
+    if material_library_path and material_map:
+        # Build lowercased material_map for matching
+        mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+        _apply_material_library(parts, material_library_path, mat_map_lower)
+        # Parts not matched by library get palette fallback
+        for i, part in enumerate(parts):
+            if not part.data.materials or len(part.data.materials) == 0:
+                _assign_palette_material(part, i)
+    else:
+        for i, part in enumerate(parts):
+            _assign_palette_material(part, i)
+
+    # ── Shadow catcher (Cycles only, template mode only) ─────────────────────
+    if shadow_catcher:
+        sc_col_name = "Shadowcatcher"
+        sc_obj_name = "Shadowcatcher"
+        # Enable the Shadowcatcher collection in all view layers
+        for vl in bpy.context.scene.view_layers:
+            def _enable_col_recursive(layer_col):
+                if layer_col.collection.name == sc_col_name:
+                    layer_col.exclude = False
+                    layer_col.collection.hide_render = False
+                    layer_col.collection.hide_viewport = False
+                    return True
+                for child in layer_col.children:
+                    if _enable_col_recursive(child):
+                        return True
+                return False
+            _enable_col_recursive(vl.layer_collection)
+
+        sc_obj = bpy.data.objects.get(sc_obj_name)
+        if sc_obj:
+            # Calculate product bbox min Z (world space)
+            all_world_corners = []
+            for part in parts:
+                for corner in part.bound_box:
+                    all_world_corners.append((part.matrix_world @ Vector(corner)).z)
+            if all_world_corners:
+                sc_obj.location.z = min(all_world_corners)
+            print(f"[blender_render] shadow catcher enabled, plane Z={sc_obj.location.z:.4f}")
+        else:
+            print(f"[blender_render] WARNING: shadow catcher object '{sc_obj_name}' not found in template")
+
+    # lighting_only: use template World/HDRI but force auto-camera UNLESS the shadow
+    # catcher is enabled — in that case the template camera is already positioned to
+    # show both the product and its shadow on the ground plane.
+    needs_auto_camera = (lighting_only and not shadow_catcher) or not bpy.context.scene.camera
+    if lighting_only and not shadow_catcher:
+        print("[blender_render] lighting_only mode: using template World/HDRI, forcing auto-camera")
+    elif needs_auto_camera:
+        print("[blender_render] WARNING: template has no camera — will create auto-camera")
+
+    # Set very close near clip on template camera for mm-scale parts (now in metres)
+    if not needs_auto_camera and bpy.context.scene.camera:
+        bpy.context.scene.camera.data.clip_start = 0.001
+
+    print(f"[blender_render] template mode: {len(parts)} parts imported into collection '{target_collection}'")
+
+else:
+    # ── MODE A: Factory settings (original behavior) ─────────────────────────
+    needs_auto_camera = True
+    bpy.ops.wm.read_factory_settings(use_empty=True)
+    parts = _import_stl(stl_path)
+    # Scale mm→m: STEP coords are mm, Blender default unit is metres
+    _scale_mm_to_m(parts)
+    # Apply render position rotation (before camera/bbox calculations)
+    _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+    for i, part in enumerate(parts):
+        _apply_smooth(part, smooth_angle)
+        _assign_palette_material(part, i)
+
+    # Apply material library on top of palette colours (same logic as Mode B).
+    # material_library_path / material_map are parsed from argv even in Mode A
+    # but were previously never used here — that was the bug.
+    if material_library_path and material_map:
+        mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+        _apply_material_library(parts, material_library_path, mat_map_lower)
+        # Parts not matched by the library keep their palette material (already set above)
+
+if needs_auto_camera:
+    # ── Combined bounding box / bounding sphere ──────────────────────────────
+    all_corners = []
+    for part in parts:
+        all_corners.extend(part.matrix_world @ Vector(c) for c in part.bound_box)
+
+    bbox_min = Vector((
+        min(v.x for v in all_corners),
+        min(v.y for v in all_corners),
+        min(v.z for v in all_corners),
+    ))
+    bbox_max = Vector((
+        max(v.x for v in all_corners),
+        max(v.y for v in all_corners),
+        max(v.z for v in all_corners),
+    ))
+
+    bbox_center    = (bbox_min + bbox_max) * 0.5
+    bbox_dims      = bbox_max - bbox_min
+    bsphere_radius = max(bbox_dims.length * 0.5, 0.001)
+
+    print(f"[blender_render] bbox_dims={tuple(round(d,4) for d in bbox_dims)}, "
+          f"bsphere_radius={bsphere_radius:.4f}, center={tuple(round(c,4) for c in bbox_center)}")
+
+    # ── Lighting — only in Mode A (factory settings) ─────────────────────────
+    # In template mode the .blend file provides its own World/HDRI lighting.
+    # Adding auto-lights would overpower the template's intended look.
+    if not use_template:
+        light_dist = bsphere_radius * 6.0
+
+        bpy.ops.object.light_add(type='SUN', location=(
+            bbox_center.x + light_dist * 0.5,
+            bbox_center.y - light_dist * 0.35,
+            bbox_center.z + light_dist,
+        ))
+        sun = bpy.context.active_object
+        sun.data.energy = 4.0
+        sun.rotation_euler = (math.radians(45), 0, math.radians(30))
+
+        bpy.ops.object.light_add(type='AREA', location=(
+            bbox_center.x - light_dist * 0.4,
+            bbox_center.y + light_dist * 0.4,
+            bbox_center.z + light_dist * 0.7,
+        ))
+        fill = bpy.context.active_object
+        fill.data.energy = max(800.0, bsphere_radius ** 2 * 2000.0)
+        fill.data.size   = max(4.0,   bsphere_radius * 4.0)
+
+    # ── Camera ───────────────────────────────────────────────────────────────
+    ELEVATION_DEG   = 28.0
+    AZIMUTH_DEG     = 40.0
+    LENS_MM         = 50.0
+    SENSOR_WIDTH_MM = 36.0
+    FILL_FACTOR     = 0.85
+
+    elevation_rad = math.radians(ELEVATION_DEG)
+    azimuth_rad   = math.radians(AZIMUTH_DEG)
+
+    cam_dir = Vector((
+        math.cos(elevation_rad) * math.cos(azimuth_rad),
+        math.cos(elevation_rad) * math.sin(azimuth_rad),
+        math.sin(elevation_rad),
+    )).normalized()
+
+    fov_h = math.atan(SENSOR_WIDTH_MM / (2.0 * LENS_MM))
+    fov_v = math.atan(SENSOR_WIDTH_MM * (height / width) / (2.0 * LENS_MM))
+    fov_used = min(fov_h, fov_v)
+
+    dist = (bsphere_radius / math.tan(fov_used)) / FILL_FACTOR
+    dist = max(dist, bsphere_radius * 1.5)
+    print(f"[blender_render] camera dist={dist:.4f}, fov={math.degrees(fov_used):.2f}°")
+
+    cam_location = bbox_center + cam_dir * dist
+    bpy.ops.object.camera_add(location=cam_location)
+    cam_obj = bpy.context.active_object
+    cam_obj.data.lens = LENS_MM
+    bpy.context.scene.camera = cam_obj
+
+    look_dir = (bbox_center - cam_location).normalized()
+    up_world = Vector((0.0, 0.0, 1.0))
+    right    = look_dir.cross(up_world)
+    if right.length < 1e-6:
+        right = Vector((1.0, 0.0, 0.0))
+    right.normalize()
+    cam_up = right.cross(look_dir).normalized()
+
+    rot_mat = Matrix((
+        ( right.x,     right.y,     right.z),
+        ( cam_up.x,    cam_up.y,    cam_up.z),
+        (-look_dir.x, -look_dir.y, -look_dir.z),
+    )).transposed()
+    cam_obj.rotation_euler = rot_mat.to_euler('XYZ')
+
+    cam_obj.data.clip_start = max(dist * 0.001, 0.0001)
+    cam_obj.data.clip_end   = dist + bsphere_radius * 3.0
+    print(f"[blender_render] clip {cam_obj.data.clip_start:.6f} … {cam_obj.data.clip_end:.4f}")
+
+    # ── World background — only in Mode A ────────────────────────────────────
+    # In template mode the .blend file owns its World (HDRI, sky texture, studio
+    # lighting).  Overwriting it would destroy the HDR look the template was
+    # designed to use (e.g. Alpha-HDR output types with Filmic tonemapping).
+    if not use_template:
+        world = bpy.data.worlds.new("World")
+        bpy.context.scene.world = world
+        world.use_nodes = True
+        bg = world.node_tree.nodes["Background"]
+        bg.inputs["Color"].default_value    = (0.96, 0.96, 0.97, 1.0)
+        bg.inputs["Strength"].default_value = 0.15
+
+# ── Render engine ─────────────────────────────────────────────────────────────
+scene = bpy.context.scene
+
+if engine == "eevee":
+    # Blender 4.x used 'BLENDER_EEVEE_NEXT'; Blender 5.x reverted to 'BLENDER_EEVEE'.
+    # Try both names so the script works across versions.
+    set_ok = False
+    for eevee_id in ('BLENDER_EEVEE', 'BLENDER_EEVEE_NEXT'):
+        try:
+            scene.render.engine = eevee_id
+            set_ok = True
+            print(f"[blender_render] EEVEE engine id: {eevee_id}")
+            break
+        except TypeError:
+            continue
+
+    if not set_ok:
+        print("[blender_render] WARNING: could not set EEVEE engine – falling back to Cycles")
+        engine = "cycles"
+
+    if engine == "eevee":
+        # Sample attribute name changed across minor versions
+        for attr in ('taa_render_samples', 'samples'):
+            try:
+                setattr(scene.eevee, attr, samples)
+                print(f"[blender_render] EEVEE samples: scene.eevee.{attr}={samples}")
+                break
+            except AttributeError:
+                continue
+
+if engine != "eevee":   # covers both explicit Cycles and EEVEE-fallback
+    scene.render.engine        = 'CYCLES'
+    scene.cycles.samples       = samples
+    scene.cycles.use_denoising = True
+    scene.cycles.denoiser = denoiser_arg if denoiser_arg else 'OPENIMAGEDENOISE'
+    if denoising_input_passes_arg:
+        try: scene.cycles.denoising_input_passes = denoising_input_passes_arg
+        except Exception: pass
+    if denoising_prefilter_arg:
+        try: scene.cycles.denoising_prefilter = denoising_prefilter_arg
+        except Exception: pass
+    if denoising_quality_arg:
+        try: scene.cycles.denoising_quality = denoising_quality_arg
+        except Exception: pass
+    if denoising_use_gpu_arg:
+        try: scene.cycles.denoising_use_gpu = (denoising_use_gpu_arg == "1")
+        except AttributeError: pass
+    if noise_threshold_arg:
+        scene.cycles.use_adaptive_sampling = True
+        scene.cycles.adaptive_threshold = float(noise_threshold_arg)
+
+    # ── Device selection: "cpu" forces CPU, "gpu" forces GPU (fail if unavailable),
+    #    "auto" tries GPU first and falls back to CPU.
+    gpu_type_found = None
+    if cycles_device != "cpu":
+        try:
+            cycles_prefs = bpy.context.preferences.addons['cycles'].preferences
+            for device_type in ('OPTIX', 'CUDA', 'HIP', 'ONEAPI'):
+                try:
+                    cycles_prefs.compute_device_type = device_type
+                    cycles_prefs.get_devices()
+                    gpu_devs = [d for d in cycles_prefs.devices if d.type != 'CPU']
+                    if gpu_devs:
+                        for d in gpu_devs:
+                            d.use = True
+                        gpu_type_found = device_type
+                        break
+                except Exception as e:
+                    print(f"[blender_render] {device_type} not available: {e}")
+        except Exception as e:
+            print(f"[blender_render] GPU probe failed: {e}")
+
+    if gpu_type_found:
+        scene.cycles.device = 'GPU'
+        print(f"[blender_render] Cycles GPU ({gpu_type_found}), samples={samples}")
+    else:
+        scene.cycles.device = 'CPU'
+        print(f"[blender_render] WARNING: GPU not found — falling back to CPU, samples={samples}")
+
+# ── Colour management ─────────────────────────────────────────────────────────
+# In template mode the .blend file owns its colour management (e.g. Filmic/
+# AgX for HDR, custom exposure for Alpha-HDR output types). Overwriting it
+# would destroy the look the template was designed for.
+# In factory-settings mode (Mode A) force Standard to avoid the grey Filmic
+# tint that Blender applies by default.
+if not use_template:
+    scene.view_settings.view_transform = 'Standard'
+    scene.view_settings.exposure        = 0.0
+    scene.view_settings.gamma           = 1.0
+    try:
+        scene.view_settings.look = 'None'
+    except Exception:
+        pass
+
+# ── Render settings ───────────────────────────────────────────────────────────
+scene.render.resolution_x               = width
+scene.render.resolution_y               = height
+scene.render.resolution_percentage      = 100
+scene.render.image_settings.file_format = 'PNG'
+scene.render.filepath                   = output_path
+scene.render.film_transparent           = transparent_bg
+
+# ── Render ────────────────────────────────────────────────────────────────────
+print(f"[blender_render] Rendering → {output_path}  (Blender {bpy.app.version_string})")
+bpy.ops.render.render(write_still=True)
+print("[blender_render] render done.")
+
+# ── Pillow post-processing: green bar + model name label ─────────────────────
+# Skip overlay for transparent renders to keep clean alpha channel
+if transparent_bg:
+    print("[blender_render] Transparent mode — skipping Pillow overlay.")
+else:
+    try:
+        from PIL import Image, ImageDraw, ImageFont
+
+        img  = Image.open(output_path).convert("RGBA")
+        draw = ImageDraw.Draw(img)
+        W, H = img.size
+
+        # Schaeffler green top bar
+        bar_h = max(8, H // 32)
+        draw.rectangle([0, 0, W - 1, bar_h - 1], fill=(0, 137, 61, 255))
+
+        # Model name strip at bottom
+        model_name = os.path.splitext(os.path.basename(stl_path))[0]
+        label_h    = max(20, H // 20)
+        img.alpha_composite(
+            Image.new("RGBA", (W, label_h), (30, 30, 30, 180)),
+            dest=(0, H - label_h),
+        )
+
+        font_size = max(10, label_h - 6)
+        font = None
+        for fp in [
+            "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf",
+            "/usr/share/fonts/truetype/liberation/LiberationSans-Bold.ttf",
+            "/usr/share/fonts/truetype/freefont/FreeSansBold.ttf",
+        ]:
+            if os.path.exists(fp):
+                try:
+                    font = ImageFont.truetype(fp, font_size)
+                    break
+                except Exception:
+                    pass
+        if font is None:
+            font = ImageFont.load_default()
+
+        tb     = draw.textbbox((0, 0), model_name, font=font)
+        text_w = tb[2] - tb[0]
+        draw.text(
+            ((W - text_w) // 2, H - label_h + (label_h - (tb[3] - tb[1])) // 2),
+            model_name, font=font, fill=(255, 255, 255, 255),
+        )
+
+        img.convert("RGB").save(output_path, format="PNG")
+        print(f"[blender_render] Pillow overlay applied.")
+
+    except ImportError:
+        print("[blender_render] Pillow not in Blender Python – skipping overlay.")
+    except Exception as exc:
+        print(f"[blender_render] Pillow overlay failed (non-fatal): {exc}")
+
+print("[blender_render] Done.")

render-worker/scripts/still_render.py

@@ -0,0 +1,781 @@
+"""Blender Python script: single-frame still render for Flamenco.
+
+Matches the lighting, camera, materials, and post-processing of the
+Celery blender_render.py so that LQ and HQ renders look consistent.
+
+Usage (from Blender):
+  blender --background --python still_render.py -- \
+    <stl_path> <output_path> <width> <height> <engine> <samples> \
+    <part_colors_json> <transparent_bg> \
+    [template_path] [target_collection] [material_library_path] [material_map_json]
+"""
+import bpy
+import sys
+import os
+import json
+import math
+from mathutils import Vector, Matrix
+
+# ── Colour palette (matches blender_render.py / Three.js renderer) ───────────
+PALETTE_HEX = [
+    "#4C9BE8", "#E85B4C", "#4CBE72", "#E8A84C", "#A04CE8",
+    "#4CD4E8", "#E84CA8", "#7EC850", "#E86B30", "#5088C8",
+]
+
+def _srgb_to_linear(c: int) -> float:
+    v = c / 255.0
+    return v / 12.92 if v <= 0.04045 else ((v + 0.055) / 1.055) ** 2.4
+
+def _hex_to_linear(hex_color: str) -> tuple:
+    h = hex_color.lstrip('#')
+    return (
+        _srgb_to_linear(int(h[0:2], 16)),
+        _srgb_to_linear(int(h[2:4], 16)),
+        _srgb_to_linear(int(h[4:6], 16)),
+        1.0,
+    )
+
+PALETTE_LINEAR = [_hex_to_linear(h) for h in PALETTE_HEX]
+
+SMOOTH_ANGLE = 30  # degrees
+
+
+# ── Helper functions ─────────────────────────────────────────────────────────
+
+def _ensure_collection(name: str):
+    """Return a collection by name, creating it if needed."""
+    if name in bpy.data.collections:
+        return bpy.data.collections[name]
+    col = bpy.data.collections.new(name)
+    bpy.context.scene.collection.children.link(col)
+    return col
+
+
+def _assign_palette_material(part_obj, index):
+    """Assign a palette colour material to a mesh part."""
+    color = PALETTE_LINEAR[index % len(PALETTE_LINEAR)]
+    mat = bpy.data.materials.new(name=f"Part_{index}")
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes.get("Principled BSDF")
+    if bsdf:
+        bsdf.inputs["Base Color"].default_value = color
+        bsdf.inputs["Metallic"].default_value = 0.35
+        bsdf.inputs["Roughness"].default_value = 0.40
+        try:
+            bsdf.inputs["Specular IOR Level"].default_value = 0.5
+        except KeyError:
+            pass
+    part_obj.data.materials.clear()
+    part_obj.data.materials.append(mat)
+
+
+def _apply_smooth(part_obj, angle_deg):
+    """Apply smooth or flat shading to a mesh object."""
+    bpy.context.view_layer.objects.active = part_obj
+    part_obj.select_set(True)
+    if angle_deg > 0:
+        try:
+            bpy.ops.object.shade_smooth_by_angle(angle=math.radians(angle_deg))
+        except AttributeError:
+            bpy.ops.object.shade_smooth()
+            part_obj.data.use_auto_smooth = True
+            part_obj.data.auto_smooth_angle = math.radians(angle_deg)
+    else:
+        bpy.ops.object.shade_flat()
+
+
+import re as _re
+
+
+def _scale_mm_to_m(parts):
+    """Scale imported STL objects from mm to Blender metres (×0.001).
+
+    STEP/STL coordinates are in mm; Blender's default unit is metres.
+    Without scaling a 50 mm part appears as 50 m inside Blender — way too large
+    relative to any template environment designed in metric units.
+    """
+    if not parts:
+        return
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.scale = (0.001, 0.001, 0.001)
+        p.location *= 0.001
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(scale=True, location=False, rotation=False)
+    print(f"[still_render] scaled {len(parts)} parts mm→m (×0.001)")
+
+
+def _apply_rotation(parts, rx, ry, rz):
+    """Apply Euler rotation (degrees, XYZ order) to all parts around world origin."""
+    if not parts or (rx == 0.0 and ry == 0.0 and rz == 0.0):
+        return
+    import math
+    from mathutils import Euler
+    rot_mat = Euler((math.radians(rx), math.radians(ry), math.radians(rz)), 'XYZ').to_matrix().to_4x4()
+    for p in parts:
+        p.matrix_world = rot_mat @ p.matrix_world
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(location=False, rotation=True, scale=False)
+    print(f"[still_render] applied rotation ({rx}°, {ry}°, {rz}°) to {len(parts)} parts")
+
+
+def _import_stl(stl_file):
+    """Import STL into Blender, using per-part STLs if available.
+
+    Checks for {stl_stem}_parts/manifest.json next to the STL file.
+    - Per-part mode: imports each part STL, names Blender object after STEP part name.
+    - Fallback: imports combined STL and splits by loose geometry.
+
+    Returns list of Blender mesh objects, centred at origin.
+    """
+    stl_dir = os.path.dirname(stl_file)
+    stl_stem = os.path.splitext(os.path.basename(stl_file))[0]
+    parts_dir = os.path.join(stl_dir, stl_stem + "_parts")
+    manifest_path = os.path.join(parts_dir, "manifest.json")
+
+    parts = []
+
+    if os.path.isfile(manifest_path):
+        # ── Per-part mode ────────────────────────────────────────────────
+        try:
+            with open(manifest_path, "r") as f:
+                manifest = json.loads(f.read())
+            part_entries = manifest.get("parts", [])
+        except Exception as e:
+            print(f"[still_render] WARNING: failed to read manifest: {e}")
+            part_entries = []
+
+        if part_entries:
+            for entry in part_entries:
+                part_file = os.path.join(parts_dir, entry["file"])
+                part_name = entry["name"]
+                if not os.path.isfile(part_file):
+                    print(f"[still_render] WARNING: part STL missing: {part_file}")
+                    continue
+
+                bpy.ops.object.select_all(action='DESELECT')
+                bpy.ops.wm.stl_import(filepath=part_file)
+                imported = bpy.context.selected_objects
+                if imported:
+                    obj = imported[0]
+                    obj.name = part_name
+                    if obj.data:
+                        obj.data.name = part_name
+                    parts.append(obj)
+
+            if parts:
+                print(f"[still_render] imported {len(parts)} named parts from per-part STLs")
+
+    # ── Fallback: combined STL + separate by loose ───────────────────────
+    if not parts:
+        bpy.ops.wm.stl_import(filepath=stl_file)
+        obj = bpy.context.selected_objects[0] if bpy.context.selected_objects else None
+        if obj is None:
+            print(f"ERROR: No objects imported from {stl_file}")
+            sys.exit(1)
+
+        bpy.context.view_layer.objects.active = obj
+        bpy.ops.object.origin_set(type='ORIGIN_GEOMETRY', center='BOUNDS')
+        obj.location = (0.0, 0.0, 0.0)
+
+        bpy.ops.object.mode_set(mode='EDIT')
+        bpy.ops.mesh.separate(type='LOOSE')
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        parts = list(bpy.context.selected_objects)
+        print(f"[still_render] fallback: separated into {len(parts)} part(s)")
+        return parts
+
+    # ── Centre per-part imports at origin (combined bbox) ────────────────
+    all_corners = []
+    for p in parts:
+        all_corners.extend(p.matrix_world @ Vector(c) for c in p.bound_box)
+
+    if all_corners:
+        mins = Vector((min(v.x for v in all_corners),
+                        min(v.y for v in all_corners),
+                        min(v.z for v in all_corners)))
+        maxs = Vector((max(v.x for v in all_corners),
+                        max(v.y for v in all_corners),
+                        max(v.z for v in all_corners)))
+        center = (mins + maxs) * 0.5
+        for p in parts:
+            p.location -= center
+
+    return parts
+
+
+def _resolve_part_name(index, part_obj, part_names_ordered):
+    """Get the STEP part name for a Blender part by index.
+
+    With per-part import, part_obj.name IS the STEP name (possibly with
+    Blender .NNN suffix). Falls back to part_names_ordered for combined-STL mode.
+    """
+    base_name = _re.sub(r'\.\d{3}$', '', part_obj.name)
+    if part_names_ordered and index < len(part_names_ordered):
+        return part_names_ordered[index]
+    return base_name
+
+
+def _apply_material_library(parts, mat_lib_path, mat_map, part_names_ordered=None):
+    """Append materials from library .blend and assign to parts via material_map.
+
+    With per-part STL import, Blender objects are named after STEP parts,
+    so matching is by name (stripping Blender .NNN suffix for duplicates).
+    Falls back to part_names_ordered index-based matching for combined-STL mode.
+
+    mat_map: {part_name_lower: material_name}
+    Parts without a match keep their current material.
+    """
+    if not mat_lib_path or not os.path.isfile(mat_lib_path):
+        print(f"[still_render] material library not found: {mat_lib_path}")
+        return
+
+    # Collect unique material names needed
+    needed = set(mat_map.values())
+    if not needed:
+        return
+
+    # Append materials from library
+    appended = {}
+    for mat_name in needed:
+        inner_path = f"{mat_lib_path}/Material/{mat_name}"
+        try:
+            bpy.ops.wm.append(
+                filepath=inner_path,
+                directory=f"{mat_lib_path}/Material/",
+                filename=mat_name,
+                link=False,
+            )
+            if mat_name in bpy.data.materials:
+                appended[mat_name] = bpy.data.materials[mat_name]
+                print(f"[still_render] appended material: {mat_name}")
+            else:
+                print(f"[still_render] WARNING: material '{mat_name}' not found after append")
+        except Exception as exc:
+            print(f"[still_render] WARNING: failed to append material '{mat_name}': {exc}")
+
+    if not appended:
+        return
+
+    # Assign materials to parts — primary: name-based (per-part STL mode),
+    # secondary: index-based via part_names_ordered (combined STL fallback)
+    assigned_count = 0
+    for i, part in enumerate(parts):
+        # Try name-based matching first (strip Blender .NNN suffix)
+        base_name = _re.sub(r'\.\d{3}$', '', part.name)
+        part_key = base_name.lower().strip()
+        mat_name = mat_map.get(part_key)
+
+        # Fall back to index-based matching via part_names_ordered
+        if not mat_name and part_names_ordered and i < len(part_names_ordered):
+            step_name = part_names_ordered[i]
+            part_key = step_name.lower().strip()
+            mat_name = mat_map.get(part_key)
+
+        if mat_name and mat_name in appended:
+            part.data.materials.clear()
+            part.data.materials.append(appended[mat_name])
+            assigned_count += 1
+            print(f"[still_render] assigned '{mat_name}' to part '{part.name}'")
+
+    print(f"[still_render] material assignment: {assigned_count}/{len(parts)} parts matched")
+
+
+def main():
+    argv = sys.argv
+    args = argv[argv.index("--") + 1:]
+
+    stl_path = args[0]
+    output_path = args[1]
+    width = int(args[2])
+    height = int(args[3])
+    engine = args[4]
+    samples = int(args[5])
+    part_colors_json = args[6] if len(args) > 6 else "{}"
+    transparent_bg = args[7] == "1" if len(args) > 7 else False
+
+    # Template + material library args (passed by schaeffler-still.js)
+    template_path = args[8] if len(args) > 8 and args[8] else ""
+    target_collection = args[9] if len(args) > 9 else "Product"
+    material_library_path = args[10] if len(args) > 10 and args[10] else ""
+    material_map_raw = args[11] if len(args) > 11 else "{}"
+    part_names_ordered_raw = args[12] if len(args) > 12 else "[]"
+    lighting_only = args[13] == "1" if len(args) > 13 else False
+    cycles_device = args[14].lower() if len(args) > 14 else "auto"  # "auto", "gpu", "cpu"
+    shadow_catcher = args[15] == "1" if len(args) > 15 else False
+    rotation_x = float(args[16]) if len(args) > 16 else 0.0
+    rotation_y = float(args[17]) if len(args) > 17 else 0.0
+    rotation_z = float(args[18]) if len(args) > 18 else 0.0
+    noise_threshold_arg = args[19] if len(args) > 19 else ""
+    denoiser_arg = args[20] if len(args) > 20 else ""
+    denoising_input_passes_arg = args[21] if len(args) > 21 else ""
+    denoising_prefilter_arg = args[22] if len(args) > 22 else ""
+    denoising_quality_arg = args[23] if len(args) > 23 else ""
+    denoising_use_gpu_arg = args[24] if len(args) > 24 else ""
+
+    os.makedirs(os.path.dirname(output_path), exist_ok=True)
+
+    try:
+        part_colors = json.loads(part_colors_json)
+    except json.JSONDecodeError:
+        part_colors = {}
+
+    try:
+        material_map = json.loads(material_map_raw) if material_map_raw else {}
+    except json.JSONDecodeError:
+        material_map = {}
+
+    try:
+        part_names_ordered = json.loads(part_names_ordered_raw) if part_names_ordered_raw else []
+    except json.JSONDecodeError:
+        part_names_ordered = []
+
+    # Validate template path: if provided it MUST exist on disk.
+    # A missing template is a configuration error — fail loudly rather than
+    # silently falling back to factory-settings mode which produces renders that
+    # look completely wrong.
+    if template_path and not os.path.isfile(template_path):
+        print(f"[still_render] ERROR: template_path was provided but file not found: {template_path}")
+        print("[still_render] Ensure the blend-templates directory is accessible on this worker.")
+        sys.exit(1)
+
+    use_template = bool(template_path)
+
+    print(f"[still_render] engine={engine}, samples={samples}, size={width}x{height}, transparent={transparent_bg}")
+    print(f"[still_render] part_names_ordered: {len(part_names_ordered)} entries")
+    if use_template:
+        print(f"[still_render] template={template_path}, collection={target_collection}, lighting_only={lighting_only}")
+    else:
+        print("[still_render] no template — using factory settings (Mode A)")
+    if material_library_path:
+        print(f"[still_render] material_library={material_library_path}, material_map keys={list(material_map.keys())}")
+
+    # ── SCENE SETUP ──────────────────────────────────────────────────────────
+
+    if use_template:
+        # ── MODE B: Template-based render ────────────────────────────────────
+        print(f"[still_render] Opening template: {template_path}")
+        bpy.ops.wm.open_mainfile(filepath=template_path)
+
+        # Find or create target collection
+        target_col = _ensure_collection(target_collection)
+
+        # Import and split STL
+        parts = _import_stl(stl_path)
+        # Scale mm→m: STEP coords are mm, Blender default unit is metres
+        _scale_mm_to_m(parts)
+        # Apply render position rotation (before camera/bbox calculations)
+        _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+        # Move imported parts into target collection
+        for part in parts:
+            for col in list(part.users_collection):
+                col.objects.unlink(part)
+            target_col.objects.link(part)
+
+        # Apply smooth shading
+        for part in parts:
+            _apply_smooth(part, SMOOTH_ANGLE)
+
+        # Material assignment: library materials if available, otherwise palette
+        if material_library_path and material_map:
+            mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+            _apply_material_library(parts, material_library_path, mat_map_lower, part_names_ordered)
+            # Parts not matched by library get palette fallback
+            for i, part in enumerate(parts):
+                if not part.data.materials or len(part.data.materials) == 0:
+                    _assign_palette_material(part, i)
+        else:
+            for i, part in enumerate(parts):
+                step_name = _resolve_part_name(i, part, part_names_ordered)
+                color_hex = part_colors.get(step_name)
+                if color_hex:
+                    color = _hex_to_linear(color_hex)
+                    mat = bpy.data.materials.new(name=f"Part_{i}")
+                    mat.use_nodes = True
+                    bsdf = mat.node_tree.nodes.get("Principled BSDF")
+                    if bsdf:
+                        bsdf.inputs["Base Color"].default_value = color
+                        bsdf.inputs["Metallic"].default_value = 0.35
+                        bsdf.inputs["Roughness"].default_value = 0.40
+                        try:
+                            bsdf.inputs["Specular IOR Level"].default_value = 0.5
+                        except KeyError:
+                            pass
+                    part.data.materials.clear()
+                    part.data.materials.append(mat)
+                else:
+                    _assign_palette_material(part, i)
+
+        # ── Shadow catcher (Cycles only, template mode only) ─────────────────
+        if shadow_catcher:
+            sc_col_name = "Shadowcatcher"
+            sc_obj_name = "Shadowcatcher"
+            for vl in bpy.context.scene.view_layers:
+                def _enable_col_recursive(layer_col):
+                    if layer_col.collection.name == sc_col_name:
+                        layer_col.exclude = False
+                        layer_col.collection.hide_render = False
+                        layer_col.collection.hide_viewport = False
+                        return True
+                    for child in layer_col.children:
+                        if _enable_col_recursive(child):
+                            return True
+                    return False
+                _enable_col_recursive(vl.layer_collection)
+
+            sc_obj = bpy.data.objects.get(sc_obj_name)
+            if sc_obj:
+                all_world_z = []
+                for part in parts:
+                    for corner in part.bound_box:
+                        all_world_z.append((part.matrix_world @ Vector(corner)).z)
+                if all_world_z:
+                    sc_obj.location.z = min(all_world_z)
+                print(f"[still_render] shadow catcher enabled, plane Z={sc_obj.location.z:.4f}")
+            else:
+                print(f"[still_render] WARNING: shadow catcher object '{sc_obj_name}' not found in template")
+
+        # lighting_only: use template World/HDRI but force auto-camera UNLESS the shadow
+        # catcher is enabled — in that case the template camera is already positioned to
+        # show both the product and its shadow on the ground plane.
+        needs_auto_camera = (lighting_only and not shadow_catcher) or not bpy.context.scene.camera
+        if lighting_only and not shadow_catcher:
+            print("[still_render] lighting_only mode: using template World/HDRI, forcing auto-camera")
+        elif needs_auto_camera:
+            print("[still_render] WARNING: template has no camera — will create auto-camera")
+
+        # Set very close near clip on template camera for mm-scale parts (now in metres)
+        if not needs_auto_camera and bpy.context.scene.camera:
+            bpy.context.scene.camera.data.clip_start = 0.001
+
+        print(f"[still_render] template mode: {len(parts)} parts imported into collection '{target_collection}'")
+
+    else:
+        # ── MODE A: Factory settings (original behavior) ─────────────────────
+        needs_auto_camera = True
+        bpy.ops.wm.read_factory_settings(use_empty=True)
+
+        parts = _import_stl(stl_path)
+        # Scale mm→m: STEP coords are mm, Blender default unit is metres
+        _scale_mm_to_m(parts)
+        # Apply render position rotation (before camera/bbox calculations)
+        _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+        for i, part in enumerate(parts):
+            _apply_smooth(part, SMOOTH_ANGLE)
+
+        # Material assignment: library materials if available, else part_colors/palette
+        if material_library_path and material_map:
+            mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+            _apply_material_library(parts, material_library_path, mat_map_lower, part_names_ordered)
+            # Palette fallback for unmatched parts
+            for i, part in enumerate(parts):
+                if not part.data.materials or len(part.data.materials) == 0:
+                    _assign_palette_material(part, i)
+        else:
+            # part_colors or palette — use index-based lookup via part_names_ordered
+            for i, part in enumerate(parts):
+                step_name = _resolve_part_name(i, part, part_names_ordered)
+                color_hex = part_colors.get(step_name)
+                if color_hex:
+                    color = _hex_to_linear(color_hex)
+                else:
+                    color = PALETTE_LINEAR[i % len(PALETTE_LINEAR)]
+
+                mat = bpy.data.materials.new(name=f"Part_{i}")
+                mat.use_nodes = True
+                bsdf = mat.node_tree.nodes.get("Principled BSDF")
+                if bsdf:
+                    bsdf.inputs["Base Color"].default_value = color
+                    bsdf.inputs["Metallic"].default_value = 0.35
+                    bsdf.inputs["Roughness"].default_value = 0.40
+                    try:
+                        bsdf.inputs["Specular IOR Level"].default_value = 0.5
+                    except KeyError:
+                        pass
+                part.data.materials.clear()
+                part.data.materials.append(mat)
+
+    if needs_auto_camera:
+        # ── Combined bounding box / bounding sphere ──────────────────────────
+        all_corners = []
+        for part in parts:
+            all_corners.extend(part.matrix_world @ Vector(c) for c in part.bound_box)
+
+        bbox_min = Vector((
+            min(v.x for v in all_corners),
+            min(v.y for v in all_corners),
+            min(v.z for v in all_corners),
+        ))
+        bbox_max = Vector((
+            max(v.x for v in all_corners),
+            max(v.y for v in all_corners),
+            max(v.z for v in all_corners),
+        ))
+
+        bbox_center = (bbox_min + bbox_max) * 0.5
+        bbox_dims = bbox_max - bbox_min
+        bsphere_radius = max(bbox_dims.length * 0.5, 0.001)
+
+        print(f"[still_render] bbox_dims={tuple(round(d, 4) for d in bbox_dims)}, "
+              f"bsphere_radius={bsphere_radius:.4f}")
+
+        # ── Lighting — only in Mode A (factory settings) ─────────────────────
+        # In template mode the .blend file provides its own World/HDRI lighting.
+        # Adding auto-lights would overpower the template's intended look.
+        if not use_template:
+            light_dist = bsphere_radius * 6.0
+
+            bpy.ops.object.light_add(type='SUN', location=(
+                bbox_center.x + light_dist * 0.5,
+                bbox_center.y - light_dist * 0.35,
+                bbox_center.z + light_dist,
+            ))
+            sun = bpy.context.active_object
+            sun.data.energy = 4.0
+            sun.rotation_euler = (math.radians(45), 0, math.radians(30))
+
+            bpy.ops.object.light_add(type='AREA', location=(
+                bbox_center.x - light_dist * 0.4,
+                bbox_center.y + light_dist * 0.4,
+                bbox_center.z + light_dist * 0.7,
+            ))
+            fill = bpy.context.active_object
+            fill.data.energy = max(800.0, bsphere_radius ** 2 * 2000.0)
+            fill.data.size = max(4.0, bsphere_radius * 4.0)
+
+        # ── Camera (isometric-style, matches blender_render.py) ──────────────
+        ELEVATION_DEG = 28.0
+        AZIMUTH_DEG = 40.0
+        LENS_MM = 50.0
+        SENSOR_WIDTH_MM = 36.0
+        FILL_FACTOR = 0.85
+
+        elevation_rad = math.radians(ELEVATION_DEG)
+        azimuth_rad = math.radians(AZIMUTH_DEG)
+
+        cam_dir = Vector((
+            math.cos(elevation_rad) * math.cos(azimuth_rad),
+            math.cos(elevation_rad) * math.sin(azimuth_rad),
+            math.sin(elevation_rad),
+        )).normalized()
+
+        fov_h = math.atan(SENSOR_WIDTH_MM / (2.0 * LENS_MM))
+        fov_v = math.atan(SENSOR_WIDTH_MM * (height / width) / (2.0 * LENS_MM))
+        fov_used = min(fov_h, fov_v)
+
+        dist = (bsphere_radius / math.tan(fov_used)) / FILL_FACTOR
+        dist = max(dist, bsphere_radius * 1.5)
+
+        cam_location = bbox_center + cam_dir * dist
+        bpy.ops.object.camera_add(location=cam_location)
+        cam_obj = bpy.context.active_object
+        cam_obj.data.lens = LENS_MM
+        bpy.context.scene.camera = cam_obj
+
+        # Look-at rotation
+        look_dir = (bbox_center - cam_location).normalized()
+        up_world = Vector((0.0, 0.0, 1.0))
+        right = look_dir.cross(up_world)
+        if right.length < 1e-6:
+            right = Vector((1.0, 0.0, 0.0))
+        right.normalize()
+        cam_up = right.cross(look_dir).normalized()
+
+        rot_mat = Matrix((
+            (right.x, right.y, right.z),
+            (cam_up.x, cam_up.y, cam_up.z),
+            (-look_dir.x, -look_dir.y, -look_dir.z),
+        )).transposed()
+        cam_obj.rotation_euler = rot_mat.to_euler('XYZ')
+
+        cam_obj.data.clip_start = max(dist * 0.001, 0.0001)
+        cam_obj.data.clip_end = dist + bsphere_radius * 3.0
+
+        # ── World background — only in Mode A ───────────────────────────────
+        # In template mode the .blend file owns its World (HDRI, sky texture,
+        # studio lighting).  Overwriting it would destroy the HDR look the
+        # template was designed to use (e.g. Alpha-HDR output types).
+        if not use_template:
+            world = bpy.data.worlds.new("World")
+            bpy.context.scene.world = world
+            world.use_nodes = True
+            bg = world.node_tree.nodes["Background"]
+            bg.inputs["Color"].default_value = (0.96, 0.96, 0.97, 1.0)
+            bg.inputs["Strength"].default_value = 0.15
+
+    # ── Colour management ────────────────────────────────────────────────────
+    # In template mode the .blend file owns its colour management settings
+    # (e.g. Filmic/AgX for HDR, custom exposure for Alpha-HDR output types).
+    # Overwriting them would destroy the look the template was designed for.
+    # In factory-settings mode (Mode A) we force Standard to avoid the grey
+    # Filmic tint that Blender applies by default.
+    scene = bpy.context.scene
+    if not use_template:
+        scene.view_settings.view_transform = 'Standard'
+        scene.view_settings.exposure = 0.0
+        scene.view_settings.gamma = 1.0
+        try:
+            scene.view_settings.look = 'None'
+        except Exception:
+            pass
+
+    # ── Render engine ────────────────────────────────────────────────────────
+    if engine == "eevee":
+        eevee_ok = False
+        for eevee_id in ('BLENDER_EEVEE', 'BLENDER_EEVEE_NEXT'):
+            try:
+                scene.render.engine = eevee_id
+                eevee_ok = True
+                print(f"[still_render] EEVEE engine id: {eevee_id}")
+                break
+            except TypeError:
+                continue
+        if eevee_ok:
+            for attr in ('taa_render_samples', 'samples'):
+                try:
+                    setattr(scene.eevee, attr, samples)
+                    break
+                except AttributeError:
+                    continue
+        else:
+            print("[still_render] WARNING: EEVEE unavailable, falling back to Cycles")
+            engine = "cycles"
+
+    if engine != "eevee":
+        scene.render.engine = 'CYCLES'
+        scene.cycles.samples = samples
+        scene.cycles.use_denoising = True
+        scene.cycles.denoiser = denoiser_arg if denoiser_arg else 'OPENIMAGEDENOISE'
+        if denoising_input_passes_arg:
+            try: scene.cycles.denoising_input_passes = denoising_input_passes_arg
+            except Exception: pass
+        if denoising_prefilter_arg:
+            try: scene.cycles.denoising_prefilter = denoising_prefilter_arg
+            except Exception: pass
+        if denoising_quality_arg:
+            try: scene.cycles.denoising_quality = denoising_quality_arg
+            except Exception: pass
+        if denoising_use_gpu_arg:
+            try: scene.cycles.denoising_use_gpu = (denoising_use_gpu_arg == "1")
+            except AttributeError: pass
+        if noise_threshold_arg:
+            scene.cycles.use_adaptive_sampling = True
+            scene.cycles.adaptive_threshold = float(noise_threshold_arg)
+        # Device selection: "cpu" forces CPU, "gpu" forces GPU (warns if unavailable),
+        # "auto" (default) tries GPU first and falls back to CPU.
+        print(f"[still_render] cycles_device={cycles_device}")
+        gpu_found = False
+        if cycles_device != "cpu":
+            try:
+                cycles_prefs = bpy.context.preferences.addons['cycles'].preferences
+                for device_type in ('OPTIX', 'CUDA', 'HIP', 'ONEAPI'):
+                    try:
+                        cycles_prefs.compute_device_type = device_type
+                        cycles_prefs.get_devices()
+                        gpu_devs = [d for d in cycles_prefs.devices if d.type != 'CPU']
+                        if gpu_devs:
+                            for d in gpu_devs:
+                                d.use = True
+                            scene.cycles.device = 'GPU'
+                            gpu_found = True
+                            print(f"[still_render] Cycles GPU ({device_type})")
+                            break
+                    except Exception:
+                        continue
+            except Exception:
+                pass
+        if not gpu_found:
+            scene.cycles.device = 'CPU'
+            print("[still_render] WARNING: GPU not found — falling back to CPU")
+
+    # ── Render settings ──────────────────────────────────────────────────────
+    scene.render.resolution_x = width
+    scene.render.resolution_y = height
+    scene.render.resolution_percentage = 100
+    scene.render.film_transparent = transparent_bg
+
+    ext = os.path.splitext(output_path)[1].lower()
+    if ext in ('.jpg', '.jpeg'):
+        scene.render.image_settings.file_format = 'JPEG'
+        scene.render.image_settings.quality = 92
+    else:
+        scene.render.image_settings.file_format = 'PNG'
+
+    scene.render.filepath = output_path
+
+    # ── Render ───────────────────────────────────────────────────────────────
+    print(f"[still_render] Rendering -> {output_path}  (Blender {bpy.app.version_string})")
+    bpy.ops.render.render(write_still=True)
+    print("[still_render] render done.")
+
+    # ── Pillow post-processing: green bar + model name label ─────────────────
+    # Skip overlay for transparent renders to keep clean alpha channel
+    if transparent_bg:
+        print("[still_render] Transparent mode — skipping Pillow overlay.")
+    else:
+        try:
+            from PIL import Image, ImageDraw, ImageFont
+
+            img = Image.open(output_path).convert("RGBA")
+            draw = ImageDraw.Draw(img)
+            W, H = img.size
+
+            # Schaeffler green top bar
+            bar_h = max(8, H // 32)
+            draw.rectangle([0, 0, W - 1, bar_h - 1], fill=(0, 137, 61, 255))
+
+            # Model name strip at bottom
+            model_name = os.path.splitext(os.path.basename(stl_path))[0]
+            label_h = max(20, H // 20)
+            img.alpha_composite(
+                Image.new("RGBA", (W, label_h), (30, 30, 30, 180)),
+                dest=(0, H - label_h),
+            )
+
+            font_size = max(10, label_h - 6)
+            font = None
+            for fp in [
+                "/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf",
+                "/usr/share/fonts/truetype/liberation/LiberationSans-Bold.ttf",
+                "/usr/share/fonts/truetype/freefont/FreeSansBold.ttf",
+            ]:
+                if os.path.exists(fp):
+                    try:
+                        font = ImageFont.truetype(fp, font_size)
+                        break
+                    except Exception:
+                        pass
+            if font is None:
+                font = ImageFont.load_default()
+
+            tb = draw.textbbox((0, 0), model_name, font=font)
+            text_w = tb[2] - tb[0]
+            draw.text(
+                ((W - text_w) // 2, H - label_h + (label_h - (tb[3] - tb[1])) // 2),
+                model_name, font=font, fill=(255, 255, 255, 255),
+            )
+
+            # Save in original format
+            if ext in ('.jpg', '.jpeg'):
+                img.convert("RGB").save(output_path, format="JPEG", quality=92)
+            else:
+                img.convert("RGB").save(output_path, format="PNG")
+            print("[still_render] Pillow overlay applied.")
+
+        except ImportError:
+            print("[still_render] Pillow not available - skipping overlay.")
+        except Exception as exc:
+            print(f"[still_render] Pillow overlay failed (non-fatal): {exc}")
+
+    print("[still_render] Done.")
+
+
+if __name__ == "__main__":
+    main()

render-worker/scripts/turntable_render.py

@@ -0,0 +1,762 @@
+"""Blender Python script: turntable animation render for Flamenco.
+
+Usage (from Blender):
+  blender --background --python turntable_render.py -- \
+    <stl_path> <frames_dir> <frame_count> <degrees> <width> <height> \
+    <engine> <samples> <part_colors_json> \
+    [template_path] [target_collection] [material_library_path] [material_map_json]
+"""
+import bpy
+import sys
+import os
+import json
+import math
+from mathutils import Vector, Matrix
+
+# ── Colour palette (matches blender_render.py / Three.js renderer) ───────────
+PALETTE_HEX = [
+    "#4C9BE8", "#E85B4C", "#4CBE72", "#E8A84C", "#A04CE8",
+    "#4CD4E8", "#E84CA8", "#7EC850", "#E86B30", "#5088C8",
+]
+
+def _srgb_to_linear(c: int) -> float:
+    v = c / 255.0
+    return v / 12.92 if v <= 0.04045 else ((v + 0.055) / 1.055) ** 2.4
+
+def _hex_to_linear(hex_color: str) -> tuple:
+    h = hex_color.lstrip('#')
+    return (
+        _srgb_to_linear(int(h[0:2], 16)),
+        _srgb_to_linear(int(h[2:4], 16)),
+        _srgb_to_linear(int(h[4:6], 16)),
+        1.0,
+    )
+
+PALETTE_LINEAR = [_hex_to_linear(h) for h in PALETTE_HEX]
+
+SMOOTH_ANGLE = 30  # degrees
+
+
+# ── Helper functions ─────────────────────────────────────────────────────────
+
+def _ensure_collection(name: str):
+    """Return a collection by name, creating it if needed."""
+    if name in bpy.data.collections:
+        return bpy.data.collections[name]
+    col = bpy.data.collections.new(name)
+    bpy.context.scene.collection.children.link(col)
+    return col
+
+
+def _assign_palette_material(part_obj, index):
+    """Assign a palette colour material to a mesh part."""
+    color = PALETTE_LINEAR[index % len(PALETTE_LINEAR)]
+    mat = bpy.data.materials.new(name=f"Part_{index}")
+    mat.use_nodes = True
+    bsdf = mat.node_tree.nodes.get("Principled BSDF")
+    if bsdf:
+        bsdf.inputs["Base Color"].default_value = color
+        bsdf.inputs["Metallic"].default_value = 0.35
+        bsdf.inputs["Roughness"].default_value = 0.40
+        try:
+            bsdf.inputs["Specular IOR Level"].default_value = 0.5
+        except KeyError:
+            pass
+    part_obj.data.materials.clear()
+    part_obj.data.materials.append(mat)
+
+
+def _apply_smooth(part_obj, angle_deg):
+    """Apply smooth or flat shading to a mesh object."""
+    bpy.context.view_layer.objects.active = part_obj
+    part_obj.select_set(True)
+    if angle_deg > 0:
+        try:
+            bpy.ops.object.shade_smooth_by_angle(angle=math.radians(angle_deg))
+        except AttributeError:
+            bpy.ops.object.shade_smooth()
+            part_obj.data.use_auto_smooth = True
+            part_obj.data.auto_smooth_angle = math.radians(angle_deg)
+    else:
+        bpy.ops.object.shade_flat()
+
+
+import re as _re
+
+
+def _apply_rotation(parts, rx, ry, rz):
+    """Apply Euler XYZ rotation (degrees) to all parts by modifying matrix_world.
+
+    Rotates around world origin, which equals the assembly centre because
+    _import_stl already centres parts there.  Applied before material assignment
+    and camera/bbox calculations so everything downstream sees the final pose.
+    """
+    if not parts or (rx == 0.0 and ry == 0.0 and rz == 0.0):
+        return
+    from mathutils import Euler
+    rot_mat = Euler((math.radians(rx), math.radians(ry), math.radians(rz)), 'XYZ').to_matrix().to_4x4()
+    for p in parts:
+        p.matrix_world = rot_mat @ p.matrix_world
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(location=False, rotation=True, scale=False)
+    print(f"[turntable_render] applied rotation ({rx}°, {ry}°, {rz}°) to {len(parts)} parts")
+
+
+def _axis_rotation(axis: str, degrees: float) -> tuple:
+    """Map turntable axis name to Euler (x, y, z) rotation in radians."""
+    rad = math.radians(degrees)
+    if axis == "world_x":
+        return (rad, 0.0, 0.0)
+    elif axis == "world_y":
+        return (0.0, rad, 0.0)
+    else:  # "world_z" default
+        return (0.0, 0.0, rad)
+
+
+def _set_fcurves_linear(action):
+    """Set LINEAR interpolation on all fcurves.
+
+    Handles both the legacy Blender < 4.4 API (action.fcurves) and the new
+    Baklava layered-action API introduced in Blender 4.4 / 5.x
+    (action.layers[*].strips[*].channelbags[*].fcurves).
+    """
+    try:
+        # New layered-action API (Blender 4.4+ / 5.x)
+        for layer in action.layers:
+            for strip in layer.strips:
+                for channelbag in strip.channelbags:
+                    for fc in channelbag.fcurves:
+                        for kp in fc.keyframe_points:
+                            kp.interpolation = 'LINEAR'
+    except AttributeError:
+        # Legacy API (Blender < 4.4)
+        for fc in action.fcurves:
+            for kp in fc.keyframe_points:
+                kp.interpolation = 'LINEAR'
+
+
+def _scale_mm_to_m(parts):
+    """Scale imported STL objects from mm to Blender metres (×0.001).
+
+    STEP/STL coordinates are in mm; Blender's default unit is metres.
+    Without scaling a 50 mm part appears as 50 m inside Blender — way too large
+    relative to any template environment designed in metric units.
+    """
+    if not parts:
+        return
+    bpy.ops.object.select_all(action='DESELECT')
+    for p in parts:
+        p.scale = (0.001, 0.001, 0.001)
+        p.location *= 0.001
+        p.select_set(True)
+    bpy.context.view_layer.objects.active = parts[0]
+    bpy.ops.object.transform_apply(scale=True, location=False, rotation=False)
+    print(f"[turntable_render] scaled {len(parts)} parts mm→m (×0.001)")
+
+
+def _import_stl(stl_file):
+    """Import STL into Blender, using per-part STLs if available.
+
+    Checks for {stl_stem}_parts/manifest.json next to the STL file.
+    - Per-part mode: imports each part STL, names Blender object after STEP part name.
+    - Fallback: imports combined STL and splits by loose geometry.
+
+    Returns list of Blender mesh objects, centred at origin.
+    """
+    stl_dir = os.path.dirname(stl_file)
+    stl_stem = os.path.splitext(os.path.basename(stl_file))[0]
+    parts_dir = os.path.join(stl_dir, stl_stem + "_parts")
+    manifest_path = os.path.join(parts_dir, "manifest.json")
+
+    parts = []
+
+    if os.path.isfile(manifest_path):
+        # ── Per-part mode ────────────────────────────────────────────────
+        try:
+            with open(manifest_path, "r") as f:
+                manifest = json.loads(f.read())
+            part_entries = manifest.get("parts", [])
+        except Exception as e:
+            print(f"[turntable_render] WARNING: failed to read manifest: {e}")
+            part_entries = []
+
+        if part_entries:
+            for entry in part_entries:
+                part_file = os.path.join(parts_dir, entry["file"])
+                part_name = entry["name"]
+                if not os.path.isfile(part_file):
+                    print(f"[turntable_render] WARNING: part STL missing: {part_file}")
+                    continue
+
+                bpy.ops.object.select_all(action='DESELECT')
+                bpy.ops.wm.stl_import(filepath=part_file)
+                imported = bpy.context.selected_objects
+                if imported:
+                    obj = imported[0]
+                    obj.name = part_name
+                    if obj.data:
+                        obj.data.name = part_name
+                    parts.append(obj)
+
+            if parts:
+                print(f"[turntable_render] imported {len(parts)} named parts from per-part STLs")
+
+    # ── Fallback: combined STL + separate by loose ───────────────────────
+    if not parts:
+        bpy.ops.wm.stl_import(filepath=stl_file)
+        obj = bpy.context.selected_objects[0] if bpy.context.selected_objects else None
+        if obj is None:
+            print(f"ERROR: No objects imported from {stl_file}")
+            sys.exit(1)
+
+        bpy.context.view_layer.objects.active = obj
+        bpy.ops.object.origin_set(type='ORIGIN_GEOMETRY', center='BOUNDS')
+        obj.location = (0.0, 0.0, 0.0)
+
+        bpy.ops.object.mode_set(mode='EDIT')
+        bpy.ops.mesh.separate(type='LOOSE')
+        bpy.ops.object.mode_set(mode='OBJECT')
+
+        parts = list(bpy.context.selected_objects)
+        print(f"[turntable_render] fallback: separated into {len(parts)} part(s)")
+        return parts
+
+    # ── Centre per-part imports at origin (combined bbox) ────────────────
+    all_corners = []
+    for p in parts:
+        all_corners.extend(p.matrix_world @ Vector(c) for c in p.bound_box)
+
+    if all_corners:
+        mins = Vector((min(v.x for v in all_corners),
+                        min(v.y for v in all_corners),
+                        min(v.z for v in all_corners)))
+        maxs = Vector((max(v.x for v in all_corners),
+                        max(v.y for v in all_corners),
+                        max(v.z for v in all_corners)))
+        center = (mins + maxs) * 0.5
+        for p in parts:
+            p.location -= center
+
+    return parts
+
+
+def _resolve_part_name(index, part_obj, part_names_ordered):
+    """Get the STEP part name for a Blender part by index.
+
+    With per-part import, part_obj.name IS the STEP name (possibly with
+    Blender .NNN suffix). Falls back to part_names_ordered for combined-STL mode.
+    """
+    base_name = _re.sub(r'\.\d{3}$', '', part_obj.name)
+    if part_names_ordered and index < len(part_names_ordered):
+        return part_names_ordered[index]
+    return base_name
+
+
+def _apply_material_library(parts, mat_lib_path, mat_map, part_names_ordered=None):
+    """Append materials from library .blend and assign to parts via material_map.
+
+    With per-part STL import, Blender objects are named after STEP parts,
+    so matching is by name (stripping Blender .NNN suffix for duplicates).
+    Falls back to part_names_ordered index-based matching for combined-STL mode.
+
+    mat_map: {part_name_lower: material_name}
+    Parts without a match keep their current material.
+    """
+    if not mat_lib_path or not os.path.isfile(mat_lib_path):
+        print(f"[turntable_render] material library not found: {mat_lib_path}")
+        return
+
+    # Collect unique material names needed
+    needed = set(mat_map.values())
+    if not needed:
+        return
+
+    # Append materials from library
+    appended = {}
+    for mat_name in needed:
+        inner_path = f"{mat_lib_path}/Material/{mat_name}"
+        try:
+            bpy.ops.wm.append(
+                filepath=inner_path,
+                directory=f"{mat_lib_path}/Material/",
+                filename=mat_name,
+                link=False,
+            )
+            if mat_name in bpy.data.materials:
+                appended[mat_name] = bpy.data.materials[mat_name]
+                print(f"[turntable_render] appended material: {mat_name}")
+            else:
+                print(f"[turntable_render] WARNING: material '{mat_name}' not found after append")
+        except Exception as exc:
+            print(f"[turntable_render] WARNING: failed to append material '{mat_name}': {exc}")
+
+    if not appended:
+        return
+
+    # Assign materials to parts — primary: name-based (per-part STL mode),
+    # secondary: index-based via part_names_ordered (combined STL fallback)
+    assigned_count = 0
+    for i, part in enumerate(parts):
+        # Try name-based matching first (strip Blender .NNN suffix)
+        base_name = _re.sub(r'\.\d{3}$', '', part.name)
+        part_key = base_name.lower().strip()
+        mat_name = mat_map.get(part_key)
+
+        # Fall back to index-based matching via part_names_ordered
+        if not mat_name and part_names_ordered and i < len(part_names_ordered):
+            step_name = part_names_ordered[i]
+            part_key = step_name.lower().strip()
+            mat_name = mat_map.get(part_key)
+
+        if mat_name and mat_name in appended:
+            part.data.materials.clear()
+            part.data.materials.append(appended[mat_name])
+            assigned_count += 1
+            print(f"[turntable_render] assigned '{mat_name}' to part '{part.name}'")
+
+    print(f"[turntable_render] material assignment: {assigned_count}/{len(parts)} parts matched")
+
+
+def main():
+    argv = sys.argv
+    # Everything after "--" is our args
+    args = argv[argv.index("--") + 1:]
+
+    stl_path = args[0]
+    frames_dir = args[1]
+    frame_count = int(args[2])
+    degrees = int(args[3])
+    width = int(args[4])
+    height = int(args[5])
+    engine = args[6]
+    samples = int(args[7])
+    part_colors_json = args[8] if len(args) > 8 else "{}"
+
+    # Template + material library args (passed by schaeffler-turntable.js)
+    template_path = args[9] if len(args) > 9 and args[9] else ""
+    target_collection = args[10] if len(args) > 10 else "Product"
+    material_library_path = args[11] if len(args) > 11 and args[11] else ""
+    material_map_raw = args[12] if len(args) > 12 else "{}"
+    part_names_ordered_raw = args[13] if len(args) > 13 else "[]"
+    lighting_only = args[14] == "1" if len(args) > 14 else False
+    cycles_device = args[15].lower() if len(args) > 15 else "auto"  # "auto", "gpu", "cpu"
+    shadow_catcher = args[16] == "1" if len(args) > 16 else False
+    rotation_x = float(args[17]) if len(args) > 17 else 0.0
+    rotation_y = float(args[18]) if len(args) > 18 else 0.0
+    rotation_z = float(args[19]) if len(args) > 19 else 0.0
+    turntable_axis = args[20] if len(args) > 20 else "world_z"
+    bg_color = args[21] if len(args) > 21 else ""
+    transparent_bg = args[22] == "1" if len(args) > 22 else False
+
+    os.makedirs(frames_dir, exist_ok=True)
+
+    try:
+        part_colors = json.loads(part_colors_json)
+    except json.JSONDecodeError:
+        part_colors = {}
+
+    try:
+        material_map = json.loads(material_map_raw) if material_map_raw else {}
+    except json.JSONDecodeError:
+        material_map = {}
+
+    try:
+        part_names_ordered = json.loads(part_names_ordered_raw) if part_names_ordered_raw else []
+    except json.JSONDecodeError:
+        part_names_ordered = []
+
+    # Validate template path: if provided it MUST exist on disk.
+    if template_path and not os.path.isfile(template_path):
+        print(f"[turntable_render] ERROR: template_path was provided but file not found: {template_path}")
+        print("[turntable_render] Ensure the blend-templates directory is accessible on this worker.")
+        sys.exit(1)
+
+    use_template = bool(template_path)
+
+    print(f"[turntable_render] engine={engine}, samples={samples}, size={width}x{height}, "
+          f"frames={frame_count}, degrees={degrees}")
+    print(f"[turntable_render] part_names_ordered: {len(part_names_ordered)} entries")
+    if use_template:
+        print(f"[turntable_render] template={template_path}, collection={target_collection}, lighting_only={lighting_only}")
+    else:
+        print("[turntable_render] no template — using factory settings (Mode A)")
+    if material_library_path:
+        print(f"[turntable_render] material_library={material_library_path}, material_map keys={list(material_map.keys())}")
+
+    # ── SCENE SETUP ──────────────────────────────────────────────────────────
+
+    if use_template:
+        # ── MODE B: Template-based render ────────────────────────────────────
+        print(f"[turntable_render] Opening template: {template_path}")
+        bpy.ops.wm.open_mainfile(filepath=template_path)
+
+        # Find or create target collection
+        target_col = _ensure_collection(target_collection)
+
+        # Import and split STL
+        parts = _import_stl(stl_path)
+        # Scale mm→m: STEP coords are mm, Blender default unit is metres
+        _scale_mm_to_m(parts)
+        # Apply render position rotation before material/camera setup
+        _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+        # Move imported parts into target collection
+        for part in parts:
+            for col in list(part.users_collection):
+                col.objects.unlink(part)
+            target_col.objects.link(part)
+
+        # Apply smooth shading
+        for part in parts:
+            _apply_smooth(part, SMOOTH_ANGLE)
+
+        # Material assignment: library materials if available, otherwise palette
+        if material_library_path and material_map:
+            mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+            _apply_material_library(parts, material_library_path, mat_map_lower, part_names_ordered)
+            # Parts not matched by library get palette fallback
+            for i, part in enumerate(parts):
+                if not part.data.materials or len(part.data.materials) == 0:
+                    _assign_palette_material(part, i)
+        else:
+            for i, part in enumerate(parts):
+                step_name = _resolve_part_name(i, part, part_names_ordered)
+                color_hex = part_colors.get(step_name)
+                if not color_hex:
+                    _assign_palette_material(part, i)
+
+        # ── Shadow catcher (Cycles only, template mode only) ─────────────────
+        if shadow_catcher:
+            sc_col_name = "Shadowcatcher"
+            sc_obj_name = "Shadowcatcher"
+            for vl in bpy.context.scene.view_layers:
+                def _enable_col_recursive(layer_col):
+                    if layer_col.collection.name == sc_col_name:
+                        layer_col.exclude = False
+                        layer_col.collection.hide_render = False
+                        layer_col.collection.hide_viewport = False
+                        return True
+                    for child in layer_col.children:
+                        if _enable_col_recursive(child):
+                            return True
+                    return False
+                _enable_col_recursive(vl.layer_collection)
+
+            sc_obj = bpy.data.objects.get(sc_obj_name)
+            if sc_obj:
+                all_world_z = []
+                for part in parts:
+                    for corner in part.bound_box:
+                        all_world_z.append((part.matrix_world @ Vector(corner)).z)
+                if all_world_z:
+                    sc_obj.location.z = min(all_world_z)
+                print(f"[turntable_render] shadow catcher enabled, plane Z={sc_obj.location.z:.4f}")
+            else:
+                print(f"[turntable_render] WARNING: shadow catcher object '{sc_obj_name}' not found in template")
+
+        # lighting_only: always use auto-framing; normal template: use camera if present
+        needs_auto_camera = (lighting_only and not shadow_catcher) or not bpy.context.scene.camera
+        if lighting_only and not shadow_catcher:
+            print("[turntable_render] lighting_only mode: using template World/HDRI, forcing auto-camera")
+        elif needs_auto_camera:
+            print("[turntable_render] WARNING: template has no camera — will create auto-camera")
+
+        # Set very close near clip on template camera for mm-scale parts (now in metres)
+        if not needs_auto_camera and bpy.context.scene.camera:
+            bpy.context.scene.camera.data.clip_start = 0.001
+
+        print(f"[turntable_render] template mode: {len(parts)} parts imported into collection '{target_collection}'")
+
+    else:
+        # ── MODE A: Factory settings ─────────────────────────────────────────
+        needs_auto_camera = True
+        bpy.ops.wm.read_factory_settings(use_empty=True)
+
+        parts = _import_stl(stl_path)
+        # Scale mm→m: STEP coords are mm, Blender default unit is metres
+        _scale_mm_to_m(parts)
+        # Apply render position rotation before material/camera setup
+        _apply_rotation(parts, rotation_x, rotation_y, rotation_z)
+
+        for i, part in enumerate(parts):
+            _apply_smooth(part, SMOOTH_ANGLE)
+
+        # Material assignment: library materials if available, else part_colors/palette
+        if material_library_path and material_map:
+            mat_map_lower = {k.lower(): v for k, v in material_map.items()}
+            _apply_material_library(parts, material_library_path, mat_map_lower, part_names_ordered)
+            # Palette fallback for unmatched parts
+            for i, part in enumerate(parts):
+                if not part.data.materials or len(part.data.materials) == 0:
+                    _assign_palette_material(part, i)
+        else:
+            # part_colors or palette — use index-based lookup via part_names_ordered
+            for i, part in enumerate(parts):
+                step_name = _resolve_part_name(i, part, part_names_ordered)
+                color_hex = part_colors.get(step_name)
+                if color_hex:
+                    mat = bpy.data.materials.new(name=f"mat_{part.name}")
+                    mat.use_nodes = True
+                    bsdf = mat.node_tree.nodes.get("Principled BSDF")
+                    if bsdf:
+                        color = _hex_to_linear(color_hex)
+                        bsdf.inputs["Base Color"].default_value = color
+                        bsdf.inputs["Metallic"].default_value = 0.35
+                        bsdf.inputs["Roughness"].default_value = 0.40
+                        try:
+                            bsdf.inputs["Specular IOR Level"].default_value = 0.5
+                        except KeyError:
+                            pass
+                    part.data.materials.clear()
+                    part.data.materials.append(mat)
+                else:
+                    _assign_palette_material(part, i)
+
+    if needs_auto_camera:
+        # ── Combined bounding box / bounding sphere ──────────────────────────
+        all_corners = []
+        for part in parts:
+            all_corners.extend(part.matrix_world @ Vector(c) for c in part.bound_box)
+
+        bbox_min = Vector((
+            min(v.x for v in all_corners),
+            min(v.y for v in all_corners),
+            min(v.z for v in all_corners),
+        ))
+        bbox_max = Vector((
+            max(v.x for v in all_corners),
+            max(v.y for v in all_corners),
+            max(v.z for v in all_corners),
+        ))
+
+        bbox_center = (bbox_min + bbox_max) * 0.5
+        bbox_dims = bbox_max - bbox_min
+        bsphere_radius = max(bbox_dims.length * 0.5, 0.001)
+
+        print(f"[turntable_render] bbox_dims={tuple(round(d, 4) for d in bbox_dims)}, "
+              f"bsphere_radius={bsphere_radius:.4f}")
+
+        # ── Lighting — only in Mode A (factory settings) ─────────────────────
+        # In template mode the .blend file provides its own World/HDRI lighting.
+        # Adding auto-lights would overpower the template's intended look.
+        if not use_template:
+            light_dist = bsphere_radius * 6.0
+
+            bpy.ops.object.light_add(type='SUN', location=(
+                bbox_center.x + light_dist * 0.5,
+                bbox_center.y - light_dist * 0.35,
+                bbox_center.z + light_dist,
+            ))
+            sun = bpy.context.active_object
+            sun.data.energy = 4.0
+            sun.rotation_euler = (math.radians(45), 0, math.radians(30))
+
+            bpy.ops.object.light_add(type='AREA', location=(
+                bbox_center.x - light_dist * 0.4,
+                bbox_center.y + light_dist * 0.4,
+                bbox_center.z + light_dist * 0.7,
+            ))
+            fill = bpy.context.active_object
+            fill.data.energy = max(800.0, bsphere_radius ** 2 * 2000.0)
+            fill.data.size = max(4.0, bsphere_radius * 4.0)
+
+        # ── Camera ───────────────────────────────────────────────────────────
+        cam_dist = bsphere_radius * 2.5
+        cam_location = Vector((
+            bbox_center.x + cam_dist,
+            bbox_center.y,
+            bbox_center.z + bsphere_radius * 0.5,
+        ))
+        bpy.ops.object.camera_add(location=cam_location)
+        camera = bpy.context.active_object
+        bpy.context.scene.camera = camera
+        camera.data.clip_start = max(cam_dist * 0.001, 0.0001)
+        camera.data.clip_end = cam_dist * 10.0
+
+        # Track-to constraint for look-at
+        empty = bpy.data.objects.new("target", None)
+        bpy.context.collection.objects.link(empty)
+        empty.location = bbox_center
+
+        track = camera.constraints.new(type='TRACK_TO')
+        track.target = empty
+        track.track_axis = 'TRACK_NEGATIVE_Z'
+        track.up_axis = 'UP_Y'
+
+        # ── World background — only in Mode A ───────────────────────────────
+        # In template mode the .blend file owns its World (HDRI, sky texture,
+        # studio lighting).  Overwriting it would destroy the HDR look.
+        if not use_template:
+            world = bpy.data.worlds.new("World")
+            bpy.context.scene.world = world
+            world.use_nodes = True
+            bg = world.node_tree.nodes["Background"]
+            bg.inputs["Color"].default_value = (0.96, 0.96, 0.97, 1.0)
+            bg.inputs["Strength"].default_value = 0.15
+
+        # ── Turntable pivot ──────────────────────────────────────────────────
+        pivot = bpy.data.objects.new("pivot", None)
+        bpy.context.collection.objects.link(pivot)
+        pivot.location = bbox_center
+
+        # Parent camera to pivot
+        camera.parent = pivot
+        camera.location = (cam_dist, 0, bsphere_radius * 0.5)
+
+        # Keyframe pivot rotation
+        scene = bpy.context.scene
+        scene.frame_start = 1
+        scene.frame_end = frame_count
+
+        pivot.rotation_euler = (0, 0, 0)
+        pivot.keyframe_insert(data_path="rotation_euler", frame=1)
+        pivot.rotation_euler = _axis_rotation(turntable_axis, degrees)
+        pivot.keyframe_insert(data_path="rotation_euler", frame=frame_count + 1)
+
+        # Linear interpolation — frame N+1 is never rendered, giving N uniform steps
+        _set_fcurves_linear(pivot.animation_data.action)
+
+    else:
+        # Template has camera — set up turntable on the model parts instead
+        scene = bpy.context.scene
+        scene.frame_start = 1
+        scene.frame_end = frame_count
+
+        # Calculate model center for pivot
+        all_corners = []
+        for part in parts:
+            all_corners.extend(part.matrix_world @ Vector(c) for c in part.bound_box)
+
+        bbox_center = Vector((
+            (min(v.x for v in all_corners) + max(v.x for v in all_corners)) * 0.5,
+            (min(v.y for v in all_corners) + max(v.y for v in all_corners)) * 0.5,
+            (min(v.z for v in all_corners) + max(v.z for v in all_corners)) * 0.5,
+        ))
+
+        # Create a pivot empty and parent all parts to it
+        pivot = bpy.data.objects.new("turntable_pivot", None)
+        bpy.context.collection.objects.link(pivot)
+        pivot.location = bbox_center
+
+        for part in parts:
+            part.parent = pivot
+
+        # Keyframe pivot rotation
+        pivot.rotation_euler = (0, 0, 0)
+        pivot.keyframe_insert(data_path="rotation_euler", frame=1)
+        pivot.rotation_euler = _axis_rotation(turntable_axis, degrees)
+        pivot.keyframe_insert(data_path="rotation_euler", frame=frame_count + 1)
+
+        # Linear interpolation — frame N+1 is never rendered, giving N uniform steps
+        _set_fcurves_linear(pivot.animation_data.action)
+
+    # ── Colour management ────────────────────────────────────────────────────
+    # In template mode the .blend file owns its colour management settings.
+    # Overwriting them would destroy the intended HDR/tonemapping look.
+    # In factory-settings mode force Standard to avoid the grey Filmic tint.
+    scene = bpy.context.scene
+    if not use_template:
+        scene.view_settings.view_transform = 'Standard'
+        scene.view_settings.exposure = 0.0
+        scene.view_settings.gamma = 1.0
+        try:
+            scene.view_settings.look = 'None'
+        except Exception:
+            pass
+
+    # ── Render engine ────────────────────────────────────────────────────────
+    if engine == "eevee":
+        eevee_ok = False
+        for eevee_id in ('BLENDER_EEVEE', 'BLENDER_EEVEE_NEXT'):
+            try:
+                scene.render.engine = eevee_id
+                eevee_ok = True
+                print(f"[turntable_render] EEVEE engine id: {eevee_id}")
+                break
+            except TypeError:
+                continue
+        if eevee_ok:
+            for attr in ('taa_render_samples', 'samples'):
+                try:
+                    setattr(scene.eevee, attr, samples)
+                    break
+                except AttributeError:
+                    continue
+        else:
+            print("[turntable_render] WARNING: EEVEE not available, falling back to Cycles")
+            engine = "cycles"
+
+    if engine != "eevee":
+        scene.render.engine = 'CYCLES'
+        scene.cycles.samples = samples
+        scene.cycles.use_denoising = True
+        scene.cycles.denoiser = 'OPENIMAGEDENOISE'  # GPU-accelerated when CUDA/OptiX active
+        # Device selection: "cpu" forces CPU, "gpu" forces GPU (warns if unavailable),
+        # "auto" (default) tries GPU first and falls back to CPU.
+        print(f"[turntable_render] cycles_device={cycles_device}")
+        gpu_found = False
+        if cycles_device != "cpu":
+            try:
+                cycles_prefs = bpy.context.preferences.addons['cycles'].preferences
+                for device_type in ('OPTIX', 'CUDA', 'HIP', 'ONEAPI'):
+                    try:
+                        cycles_prefs.compute_device_type = device_type
+                        cycles_prefs.get_devices()
+                        gpu_devs = [d for d in cycles_prefs.devices if d.type != 'CPU']
+                        if gpu_devs:
+                            for d in gpu_devs:
+                                d.use = True
+                            scene.cycles.device = 'GPU'
+                            gpu_found = True
+                            print(f"[turntable_render] Cycles GPU ({device_type})")
+                            break
+                    except Exception:
+                        continue
+            except Exception:
+                pass
+        if not gpu_found:
+            scene.cycles.device = 'CPU'
+            print("[turntable_render] WARNING: GPU not found — falling back to CPU")
+
+    # ── Render settings ──────────────────────────────────────────────────────
+    scene.render.resolution_x = width
+    scene.render.resolution_y = height
+    scene.render.resolution_percentage = 100
+    scene.render.image_settings.file_format = 'PNG'
+
+    # ── Transparent background ────────────────────────────────────────────────
+    # bg_color compositing is handled by FFmpeg in the compose-video task.
+    # Blender renders transparent PNG frames when bg_color is set.
+    if bg_color or transparent_bg:
+        scene.render.film_transparent = True
+        if bg_color:
+            print(f"[turntable_render] film_transparent=True for FFmpeg bg_color compositing ({bg_color})")
+        else:
+            print("[turntable_render] transparent_bg enabled (alpha PNG frames)")
+
+    # ── Render all frames ────────────────────────────────────────────────────
+    # Per-frame loop with write_still=True.  In a single Blender session,
+    # Cycles keeps the GPU scene (BVH, textures, material graph) loaded
+    # between frames — only the animated pivot transform is updated each step.
+    # bpy.ops.render.render(animation=True) does NOT work reliably in
+    # background mode after wm.open_mainfile() in Blender 5.x (silently
+    # writes no files), so we use the explicit per-frame approach.
+    import time as _time
+    _render_start = _time.time()
+    for frame in range(1, frame_count + 1):
+        scene.frame_set(frame)
+        scene.render.filepath = os.path.join(frames_dir, f"frame_{frame:04d}")
+        bpy.ops.render.render(write_still=True)
+        elapsed = _time.time() - _render_start
+        fps_so_far = frame / elapsed
+        print(f"[turntable_render] Frame {frame}/{frame_count} — {elapsed:.1f}s elapsed ({fps_so_far:.2f} fps)")
+
+    total = _time.time() - _render_start
+    print(f"[turntable_render] Turntable render complete: {frame_count} frames in {total:.1f}s ({frame_count/total:.2f} fps avg)")
+
+
+if __name__ == "__main__":
+    main()