Texture Baking (Cycles)

The execution model is in blender-core. UVs come from blender-retopology-uv and materials from blender-pbr-materials.

One call

scripts/bake_maps.py -- --low SM_Crate --high Crate_high Crate_bolts --maps normal ao curvature id \
   --res 2048 --samples 64 --margin-px 16 --pack-orm --out //textures

Self-bake (procedural → textures, no --high): --low SM_Crate --maps basecolor roughness metallic normal --pack-orm. The script picks the GPU (OptiX/CUDA/HIP/Metal/oneAPI) and falls back to CPU, creates the target images with correct color spaces, cleans up its temporary nodes, and saves T_<name>_<N|AO|CURV|BC|R|M|ORM...>.png.

Preparation checklist (most bake bugs come from this list)

1. Low poly: UVs unwrapped, no overlaps (stacked/mirrored islands moved +1 U), padding ≥ 8 px at the bake resolution, scale applied.
2. Hard edges = UV seams on the low poly. Use either smooth shading with the bake handling gradients, or hard edges split at seams. Never put a hard edge inside a UV island.
3. Triangulate the low poly the same way the engine will, or export the triangulated mesh. Mismatched triangulation shows as shading seams.
4. High poly covers the low completely and pokes out of it only a little. Floaters (bolts, panel details) can hover just above the surface, but must stay within the extrusion distance.
5. Names: X_low / X_high pairs. Bake per part, or explode the parts apart (move each pair along an axis) so neighbouring parts don't project onto each other, then put them back.
6. Apply modifiers on the high poly as needed (multires and subd are evaluated automatically).

Rays: extrusion vs cage

• --extrusion (meters) pushes the ray origin outward from the low surface. It must be greater than the farthest distance the high poly sticks out of the low. The default is 2% of the low's diagonal; max_ray_distance is 2 × extrusion.
• Cage (--cage Crate_cage): a copy of the low with the same topology, inflated (Displace/"Push"). Use it when uniform extrusion fails (sharp concave corners, thin parts). Edit the cage locally where rays miss.
• Too small: holes or missing details. Too large: other parts of the mesh project in (intersections, "ghosting").

Map guide

Fixing common artifacts

Baking non-PBR data

• Vertex colors: bake.target = "VERTEX_COLORS" with an active color attribute (useful for mobile and Roblox-free shading).
• Lightmaps: bake combined onto UV2 (--uv-layer UVMap_Lightmap) with the scene lights.
• Multires (no separate high object): bake.use_multires=True, bake.type="NORMALS"|"DISPLACEMENT"|"VECTOR_DISPLACEMENT", bake.use_lores_mesh=True, then bpy.ops.object.bake_image(). The viewport level is the low, the sculpt level is the high.

Gotchas

• The target image must be the active Image Texture node in every material of the low object (the script handles this).
• Baking in Cycles uses the active UV map (--uv-layer to pick).
• Images aren't saved automatically: img.save() or save_render. Packed or internal images disappear on reload.
• 5.2: the Cycles texture cache (.tx) is for render memory and doesn't affect bake results.
• Run blender-asset-qa on low + high first, because flipped normals and floating chunks produce most bake garbage.