From c1e9a86996ea4595ccdfc218c788bbd465c9fe21 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hartmut=20N=C3=B6renberg?= <hn@hartmut-noerenberg.com>
Date: Sat, 7 Mar 2026 14:10:45 +0100
Subject: [PATCH] fix(gltf): route generate_gltf_geometry_task through Blender
 for materials + sharp edges
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Replace trimesh-only GLB export with Blender headless pipeline using
export_gltf.py. The viewer GLB and downloadable GLB now receive:
- Material substitution via the Schaeffler asset library (.blend)
- OCC-derived sharp edge data (sharp_edge_midpoints from mesh_attributes)
  marked as Blender sharp edges before export

Material map is resolved via resolve_material_map() to convert aliases
(e.g. "Steel--Stahl" → "SCHAEFFLER_010101_Steel-Bare") before passing
to Blender. Old gltf_geometry MediaAsset is replaced on each run to
avoid stale records accumulating.

Trimesh kept as fallback if Blender binary unavailable.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 LEARNINGS.md                    |   5 ++
 backend/app/tasks/step_tasks.py | 154 +++++++++++++++++++++++---------
 2 files changed, 119 insertions(+), 40 deletions(-)

diff --git a/LEARNINGS.md b/LEARNINGS.md
index d8bc64e..b4e1994 100644
--- a/LEARNINGS.md
+++ b/LEARNINGS.md
@@ -436,6 +436,11 @@ SQLAlchemy `Enum(create_type=False)` funktioniert nicht zuverlässig mit asyncpg
 
 ---
 
+### 2026-03-07 | GLB Export | Trimesh kennt keine Materialien — Blender-Pipeline ist Pflicht
+**Problem:** `generate_gltf_geometry_task` nutzte trimesh für STL→GLB. Trimesh ist eine reine Geometrie-Bibliothek: keine Material-Bibliotheken, kein OCC-Kantenmarking, kein Asset-Library-Support. Das erzeugte graue, facettierte GLB-Dateien ohne Materialien.
+**Lösung:** Task auf Blender headless (`export_gltf.py`) umgestellt. Übergibt: `material_map` (via `resolve_material_map()` aus `cad_part_materials`), `sharp_edges_json` (aus `mesh_attributes.sharp_edge_midpoints`), `asset_library_blend` (via `get_material_library_path()`). Trimesh nur noch als Fallback wenn Blender nicht verfügbar.
+**Fehler:** Der Blender-Script (`export_gltf.py`) war schon fertig implementiert — aber `generate_gltf_geometry_task` hat ihn nie aufgerufen. Skript vorhanden ≠ Skript verdrahtet. Immer prüfen ob ein Script auch von der richtigen Stelle aufgerufen wird.
+
 ### 2026-03-07 | Frontend | `<img src>` kann keine Auth-Header senden — useAuthBlob Hook nötig
 **Problem:** `<img src="/api/media/{id}/download">` schickt keine `Authorization`-Header → 401 → `imgError=true` → graues Icon in der Media Library. Betrifft alle Browser-nativen Elemente (`<img>`, `<video>`, `<audio>`).
 **Lösung:** `useAuthBlob(url, enabled)` Hook: `fetch(url, { headers: { Authorization: \`Bearer ${token}\` } })` → `URL.createObjectURL(blob)` → Blob-URL als `src` nutzen. Cleanup via `URL.revokeObjectURL` + `cancelled`-Flag gegen Race Conditions.
diff --git a/backend/app/tasks/step_tasks.py b/backend/app/tasks/step_tasks.py
index 3448082..4f08c4c 100644
--- a/backend/app/tasks/step_tasks.py
+++ b/backend/app/tasks/step_tasks.py
@@ -395,13 +395,21 @@ def generate_stl_cache(self, cad_file_id: str, quality: str):
 
 @celery_app.task(bind=True, name="app.tasks.step_tasks.generate_gltf_geometry_task", queue="thumbnail_rendering", max_retries=1)
 def generate_gltf_geometry_task(self, cad_file_id: str):
-    """Export a geometry-only GLB from the STL low-quality cache using trimesh.
+    """Export a GLB via Blender with material substitution and OCC sharp-edge data.
 
-    Creates a MediaAsset with asset_type='gltf_geometry' and cad_file_id set.
-    No Blender required — trimesh handles the STL→GLB conversion.
+    Pipeline:
+      1. Reads sharp_edge_midpoints from cad_file.mesh_attributes (from OCC extraction)
+      2. Resolves material_map via alias lookup (part_name → SCHAEFFLER library material)
+      3. Runs Blender headless with export_gltf.py: STL → GLB with library materials + sharp edges
+      4. Falls back to trimesh (geometry-only, no materials) if Blender is unavailable
+
+    Replaces the existing gltf_geometry MediaAsset for this CadFile on each run.
     """
+    import json as _json
+    import os as _os
+    import subprocess as _subprocess
     from pathlib import Path as _Path
-    from sqlalchemy import create_engine
+    from sqlalchemy import create_engine, select as _select
     from sqlalchemy.orm import Session
     from app.config import settings as app_settings
     from app.models.cad_file import CadFile
@@ -414,64 +422,130 @@ def generate_gltf_geometry_task(self, cad_file_id: str):
             logger.error("generate_gltf_geometry_task: no stored_path for %s", cad_file_id)
             return
         step_path_str = cad_file.stored_path
+        mesh_attrs = cad_file.mesh_attributes or {}
+        sharp_edge_midpoints = mesh_attrs.get("sharp_edge_midpoints", [])
 
-        # Read 3D export settings
-        from sqlalchemy import text as _text
-        _scale = float(session.execute(_text(
-            "SELECT value FROM system_settings WHERE key='gltf_scale_factor'"
-        )).scalar() or "0.001")
-        _smooth = (session.execute(_text(
-            "SELECT value FROM system_settings WHERE key='gltf_smooth_normals'"
-        )).scalar() or "true") == "true"
+        # Load product materials for this CAD file
+        from app.domains.products.models import Product
+        product = session.execute(
+            _select(Product).where(Product.cad_file_id == cad_file.id)
+        ).scalar_one_or_none()
+
+        raw_material_map: dict[str, str] = {}
+        if product and product.cad_part_materials:
+            for entry in product.cad_part_materials:
+                part_name = entry.get("part_name") or entry.get("name", "")
+                mat_name = entry.get("material_name") or entry.get("material", "")
+                if part_name and mat_name:
+                    raw_material_map[part_name] = mat_name
     eng.dispose()
 
-    log_task_event(self.request.id, f"Starting generate_gltf_geometry_task: cad_file={cad_file_id}", "info")
+    # Resolve aliases: "Steel--Stahl" → "SCHAEFFLER_010101_Steel-Bare"
+    from app.services.material_service import resolve_material_map
+    material_map = resolve_material_map(raw_material_map)
+
+    # Get asset library .blend path from system settings
+    from app.services.template_service import get_material_library_path
+    asset_library_blend = get_material_library_path()
+
     step = _Path(step_path_str)
     stl_path = step.parent / f"{step.stem}_low.stl"
     if not stl_path.exists():
         log_task_event(self.request.id, f"Failed: STL cache not found: {stl_path}", "error")
-        logger.error("generate_gltf_geometry_task: STL not found %s", stl_path)
         raise RuntimeError(f"STL cache not found: {stl_path}")
 
     output_path = step.parent / f"{step.stem}_geometry.glb"
-    try:
-        import trimesh
-        import trimesh as _trimesh
 
-        def _process_mesh(m):
-            m.apply_scale(_scale)
-            if _smooth:
+    log_task_event(
+        self.request.id,
+        f"Starting GLB export: {len(material_map)} materials, "
+        f"{len(sharp_edge_midpoints)} sharp-edge hints, "
+        f"library={'yes' if asset_library_blend else 'no'}",
+        "info",
+    )
+
+    # --- Blender path ---
+    blender_bin = _os.environ.get("BLENDER_BIN", "blender")
+    scripts_dir = _Path(_os.environ.get("RENDER_SCRIPTS_DIR", "/render-scripts"))
+    script_path = scripts_dir / "export_gltf.py"
+    blender_ok = False
+
+    if _Path(blender_bin).exists() and script_path.exists():
+        cmd = [
+            blender_bin, "--background", "--python", str(script_path), "--",
+            "--stl_path", str(stl_path),
+            "--output_path", str(output_path),
+            "--material_map", _json.dumps(material_map),
+            "--sharp_edges_json", _json.dumps(sharp_edge_midpoints),
+        ]
+        if asset_library_blend and _Path(asset_library_blend).exists():
+            cmd += ["--asset_library_blend", asset_library_blend]
+
+        try:
+            result = _subprocess.run(cmd, capture_output=True, text=True, timeout=180)
+            if result.returncode == 0 and output_path.exists() and output_path.stat().st_size > 0:
+                blender_ok = True
+                logger.info("generate_gltf_geometry_task: Blender export succeeded (%s KB)",
+                            output_path.stat().st_size // 1024)
+            else:
+                logger.warning(
+                    "Blender GLB export failed (exit %d) — falling back to trimesh.\n"
+                    "STDOUT: %s\nSTDERR: %s",
+                    result.returncode, result.stdout[-1500:], result.stderr[-500:],
+                )
+        except Exception as exc:
+            logger.warning("Blender GLB export error (%s) — falling back to trimesh", exc)
+    else:
+        logger.warning(
+            "Blender not available at '%s' or script missing at '%s' — using trimesh fallback",
+            blender_bin, script_path,
+        )
+
+    # --- Trimesh fallback (geometry only, no materials) ---
+    if not blender_ok:
+        try:
+            import trimesh
+            import trimesh as _trimesh
+
+            def _process_mesh(m):
+                m.apply_scale(0.001)
                 try:
                     _trimesh.smoothing.filter_laplacian(m, lamb=0.5, iterations=5)
                 except Exception:
-                    pass  # non-critical
+                    pass
 
-        mesh = trimesh.load(str(stl_path))
+            mesh = trimesh.load(str(stl_path))
+            if hasattr(mesh, 'geometry'):
+                for sub in mesh.geometry.values():
+                    _process_mesh(sub)
+            else:
+                _process_mesh(mesh)
+            mesh.export(str(output_path))
+            log_task_event(self.request.id, "Trimesh fallback export completed (no materials)", "done")
+        except Exception as exc:
+            log_task_event(self.request.id, f"Failed: {exc}", "error")
+            logger.error("generate_gltf_geometry_task trimesh fallback failed: %s", exc)
+            raise self.retry(exc=exc, countdown=15)
+    else:
+        log_task_event(self.request.id, f"Blender GLB export completed: {output_path.name}", "done")
 
-        if hasattr(mesh, 'geometry'):
-            # trimesh.Scene with multiple sub-meshes
-            for sub in mesh.geometry.values():
-                _process_mesh(sub)
-        else:
-            _process_mesh(mesh)
-
-        mesh.export(str(output_path))
-        log_task_event(self.request.id, f"Completed successfully: {output_path.name}", "done")
-        logger.info("generate_gltf_geometry_task: exported %s", output_path.name)
-    except Exception as exc:
-        log_task_event(self.request.id, f"Failed: {exc}", "error")
-        logger.error("generate_gltf_geometry_task failed for %s: %s", cad_file_id, exc)
-        raise self.retry(exc=exc, countdown=15)
-
-    # Create MediaAsset record
+    # --- Store MediaAsset (replace existing gltf_geometry for this cad_file) ---
     import asyncio
 
     async def _store():
         from app.database import AsyncSessionLocal
         from app.domains.media.models import MediaAsset, MediaAssetType
         from app.config import settings as _cfg
+        import uuid
         async with AsyncSessionLocal() as db:
-            import uuid
+            # Delete previous gltf_geometry assets for this cad_file to avoid stale records
+            from sqlalchemy import delete as _delete
+            await db.execute(
+                _delete(MediaAsset).where(
+                    MediaAsset.cad_file_id == uuid.UUID(cad_file_id),
+                    MediaAsset.asset_type == MediaAssetType.gltf_geometry,
+                )
+            )
             _key = str(output_path)
             _prefix = str(_cfg.upload_dir).rstrip("/") + "/"
             if _key.startswith(_prefix):
@@ -487,7 +561,7 @@ def generate_gltf_geometry_task(self, cad_file_id: str):
             await db.commit()
             return str(asset.id)
 
-    asset_id = asyncio.get_event_loop().run_until_complete(_store())
+    asset_id = asyncio.run(_store())
     logger.info("generate_gltf_geometry_task: MediaAsset %s created for cad %s", asset_id, cad_file_id)
     return {"glb_path": str(output_path), "asset_id": asset_id}