[gkjohnson]

Adds AO map and lightmap baking to the WebGPU path tracer, with a demo for each.

Strategies

• UV space camera: UVMapCamera rasterizes the atlas' triangle ids once, then each pixel's ray starts at its texel's surface. Samples are jittered within the texel and retried inside the triangle, as Cycles does.
• Shading models: AOMapShadingModel turns the first hit's distance into occlusion. LightmapShadingModel treats the texel as white diffuse so the path gathers its irradiance.
• Post process: gutters are filled, then the map is denoised with OIDN and stitched across chart seams with a port of Zalo's LightMapSeams.
• Unwrapping: UVUnwrapper packs every mesh into one atlas with xatlas (via watlas).

Future improvements

Map Generation

• Jitter the triangle id raster every frame, as three.js' LightMapper does, for smoother texels on triangle edges.
• A faster and more complete mip chain gutter fill.
• Bent normal, directional, specular occlusion, and indirect-only maps.
• A radiance cache approach.
• A port of the SVGF denoiser. Requires custom output variables in core.
• Atlas improvements: multiple pages, instances, per-mesh texel density.
• Use upstream three.js copies of classes where possible.

Core

• variance detection, stop pixels once their noise is low, rather than at a fixed sample count.
• emissive triangle sampling.
• path termination hooks, for radiance caches.
• more pluggable post-processing steps: gutter fill, stitching, denoising.

Before Merge

• Clean up "getObjectInfo"
• Upstream necessary changes / generators as much as possible to three.js
• Include support for SVGF / custom AoVs? Can be included in the shading model class?
• Path to radiance cache?

Videos

	AO Map Gen	Light Map Gen
Live demo	link	link
25spp, 20482 map generation video	aomap.mp4	lightmap.mp4