Bake static lighting

Lightmaps remove per-frame shadow and lighting cost for static lights on static geometry.

• Application registers Lightmapper; manual AppOptions bootstraps set lightmapper = Lightmapper.
• On the light, set bake = true; once every mesh it lights is lightmapped, set affectDynamic = false.
• On each mesh, set render.lightmapped = true, or it goes unlit once affectDynamic is off. Size it with lightmapSizeMultiplier; castShadowsLightmap lets meshes shadow each other.
• Set the mode on scene.lightmapMode: BAKE_COLOR for flat diffuse, or the default BAKE_COLORDIR, which adds direction for normal- or specular-mapped materials.
• Bake AO without lights with scene.ambientBake, ambientBakeNumSamples, and ambientBakeOcclusionBrightness and ambientBakeOcclusionContrast.
• The Engine bakes once on the first rendered frame. Call app.lightmapper.bake(null, mode) only for nodes added later or to re-bake.

A second UV set is required

A node bakes only when every mesh instance has SEMANTIC_TEXCOORD1. Otherwise it is skipped, with only a debug-build log, and stays dynamically lit. Primitives have the set; imported GLBs often do not. Check, then unwrap or re-export.

On-device or offline

Time bake() on the target device. Move to an offline bake shipped as textures only when it misses the startup budget or needs detail the runtime lightmapper cannot produce, and state the added download size.

Dynamic objects moving through baked light need approximated occlusion and a contact shadow, or they look pasted on. Compare verify-pixels captures in and out of baked shadow.