texturecraft/crates/bake

texturecraft-bake

Mesh-map baker: bake(&BakeRequest, &Progress) -> BakeOutput turns one texture set's UV layout into float maps (0..1, rows top → bottom), supersampled, padded and deterministic. The supersamples are processed in batches: their high-poly transfer rays, then the secondary rays of ambient occlusion, bent normals and thickness go to a rays::Tracer, then all requested maps are evaluated per sample (rayon over rows).

The rays run on the CPU (rays::CpuTracer, the oracle) or, through bake_on(&BakeRequest, &Progress, &dyn Tracer), on a GPU tracer (the render crate's gpu_bake::GpuBaker, wgpu compute shaders on the path tracer's BVH traversal). The GPU receives the same rays and per-sample rotations and casts the same secondary-ray directions, so both agree up to float rounding; when the tracer fails (no adapter, a mesh too large for it, a lost device) bake_on bakes again on the CPU. BakeOutput::tracer says where the rays ran.

With a high poly (BakeRequest::high, every high-definition mesh appended into one), each low-poly sample casts one ray from the cage (BakeRequest::cage, same triangles as the low poly) or from max_frontal in front of the surface back through it to max_rear behind (both relative to the bounding-box diagonal), along normals averaged over hard edges when average_normals is on. With BakeMatch::ByMeshName, a low-poly part only sees high-poly parts of the same name once low_suffix / high_suffix are removed (wheel_low ↔ wheel_high, case-insensitive). Every map but position and world-space direction then reads the high-poly surface that ray found (AO, thickness and bent normals cast against the high poly).

Ambient occlusion, thickness and bent normals each have their own RaySettings: ray count, max distance (relative to the bounding-box diagonal), spread angle (the full cone around the normal; 180° = the hemisphere) and distribution (cosine-weighted or uniform over the cone). Ambient occlusion can ignore back faces and limit occluders to parts of the same mesh name (SelfOcclusion::SameMeshName); bent normals follow those occluder rules and share the AO rays when their settings match.

Map	Meaning	Range
Ambient occlusion	How open the surface is (rays over the cone, distance falloff)	0 occluded … 1 open
Bent normals	Mean unoccluded direction of the bent-normal rays, world space	packed ·0.5+0.5
Thickness	Mean distance through the mesh along inward rays, relative to the max distance	0 thin … 1 thick
Curvature	Mean curvature of the position-welded mesh, or (curvature_from_normal) the divergence of the baked normal map over curvature_radius texels (0: by resolution)	0 concave … 0.5 flat … 1 convex
Normal	Tangent-space normal from the high poly (OpenGL, +Y up); flat without one	packed ·0.5+0.5
Height	High-poly offset along the ray, scaled by frontal + rear distance	0 rear … 0.5 surface … 1 front
World normal	Shading normal in world space	packed ·0.5+0.5
Position	Position in the low poly's bounding box (per axis) or bounding sphere (position_mode)	0 … 1
ID	A distinct hue per mesh part (submesh)	RGB 0 … 1
Opacity	1 where the high poly was found (times its vertex and base color alpha), 0 where the ray missed	0 … 1
Color map	The high poly's vertex colors times its materials' base color (HighPoly::base_color: factor × texture at the hit UV, bilinear in linear light), sRGB-encoded like a base color texture	RGB 0 … 1
World space direction	Facing ratio towards direction: signed (0.5 perpendicular) or positive (direction_mode)	0 away … 1 facing

Uncovered texels beyond the padding get BakedMap::neutral values. Benchmarks (2K, the 7 default maps at 64 rays): cargo test -p texturecraft-bake --release -- --ignored --nocapture bench (CPU, per-map breakdown) and cargo test -p texturecraft-render --release --lib -- --ignored --nocapture gpu_bake_speed (CPU vs GPU).