- Add export_extras=True to bpy.ops.export_scene.gltf() call
- Store schaeffler_sharp_angle_deg in scene custom props before export
→ value is embedded in scenes[0].extras in the GLB JSON chunk
→ survives import/export round-trip intact (verified: 30.0 restored)
- Add tools/restore_sharp_marks.py: companion Blender script that reads
the angle from scene.get("schaeffler_sharp_angle_deg") and re-applies
mark_sharp() + mark_seam() on all mesh objects after GLB import
GLB format cannot store per-edge sharp/seam flags natively; the visual
shading is correct via vertex splits. The extras + restore script give
users the ability to reconstruct Edit Mode markers without a second format.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
