fix: material override pipeline — pass --material-override CLI arg to Blender scripts

The initial implementation only overrode the material_map dict in the task,
but the Blender USD primvar path bypassed it. Now:
- Added --material-override named CLI arg parsed in _blender_args.py
- Both Mode A (factory) and Mode B (template) in _blender_scene_setup.py
  override usd_material_lookup and material_map when set
- Passed through full chain: task → step_processor → render_blender → CLI → Blender
- Tested: 175-part bearing rendered with single Steel-Bare material (1/1 materials)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/domains/pipeline/tasks/render_order_line.py

@@ -201,8 +201,16 @@ def render_order_line_task(self, order_line_id: str):
             # Apply global material override from OutputType (e.g. x-ray mode)
             if line.output_type and line.output_type.material_override:
                 override_mat = line.output_type.material_override
-                material_map = {k: override_mat for k in material_map}
-                emit(order_line_id, f"Material override active: all parts → {override_mat}")
+                # Build override map from existing material_map keys or from parsed STEP parts
+                override_keys = set()
+                if material_map:
+                    override_keys = set(material_map.keys())
+                if cad_file and cad_file.parsed_objects:
+                    for part_name in cad_file.parsed_objects.get("objects", []):
+                        override_keys.add(part_name)
+                material_map = {k: override_mat for k in override_keys}
+                use_materials = True
+                emit(order_line_id, f"Material override active: {len(material_map)} parts → {override_mat}")
 
             if template:
                 emit(order_line_id, f"Using render template: {template.name} (collection={template.target_collection}, material_replace={template.material_replace_enabled}, lighting_only={template.lighting_only})")
@@ -352,6 +360,7 @@ def render_order_line_task(self, order_line_id: str):
                         usd_path=usd_render_path,
                         focal_length_mm=focal_length_mm,
                         sensor_width_mm=sensor_width_mm,
+                        material_override=line.output_type.material_override if line.output_type else None,
                     )
                     success = True
                     render_log = {
@@ -410,6 +419,7 @@ def render_order_line_task(self, order_line_id: str):
                     rotation_z=rotation_z,
                     focal_length_mm=focal_length_mm,
                     sensor_width_mm=sensor_width_mm,
+                    material_override=line.output_type.material_override if line.output_type else None,
                     job_id=order_line_id,
                     order_line_id=order_line_id,
                     noise_threshold=noise_threshold,

backend/app/services/render_blender.py

@@ -94,6 +94,7 @@ def render_still(
     tessellation_engine: str = "occ",
     focal_length_mm: float | None = None,
     sensor_width_mm: float | None = None,
+    material_override: str | None = None,
 ) -> dict:
     """Convert STEP → GLB (OCC or GMSH) → PNG (Blender subprocess).
 
@@ -185,6 +186,8 @@ def render_still(
             cmd += ["--focal-length", str(focal_length_mm)]
         if sensor_width_mm is not None:
             cmd += ["--sensor-width", str(sensor_width_mm)]
+        if material_override:
+            cmd += ["--material-override", material_override]
         return cmd
 
     def _run(eng: str) -> tuple[int, list[str], list[str]]:
@@ -322,6 +325,7 @@ def render_turntable_to_file(
     tessellation_engine: str = "occ",
     focal_length_mm: float | None = None,
     sensor_width_mm: float | None = None,
+    material_override: str | None = None,
 ) -> dict:
     """Render a turntable animation: STEP → STL → N frames (Blender) → mp4 (ffmpeg).
 
@@ -408,6 +412,8 @@ def render_turntable_to_file(
         cmd += ["--focal-length", str(focal_length_mm)]
     if sensor_width_mm is not None:
         cmd += ["--sensor-width", str(sensor_width_mm)]
+    if material_override:
+        cmd += ["--material-override", material_override]
 
     log_lines: list[str] = []
 

backend/app/services/step_processor.py

@@ -893,6 +893,7 @@ def render_to_file(
     tessellation_engine: str | None = None,
     focal_length_mm: float | None = None,
     sensor_width_mm: float | None = None,
+    material_override: str | None = None,
 ) -> tuple[bool, dict]:
     """Render a STEP file to a specific output path using current system settings.
 
@@ -1031,6 +1032,7 @@ def render_to_file(
                     tessellation_engine=tessellation_engine or settings["tessellation_engine"],
                     focal_length_mm=focal_length_mm,
                     sensor_width_mm=sensor_width_mm,
+                    material_override=material_override,
                 )
                 rendered_png = tmp_png if tmp_png.exists() else None
             except Exception as exc: