Lightmap and Ambient Occlusion Baking for VR Games

Baking lighting and ambient occlusion maps for VR games

Realtime global illumination in mobile VR – dream that shatters against 6.9 ms per frame. Quest 3 has neither Lumen nor decent SSAO without frame drops. Only way to get rich lighting with complex shadows and contact AO – bake it beforehand.

But baked lighting in VR has its own pitfalls absent on flat screen.

Why standard Unity Lightmapping breaks in VR

Lightmap seam stitching – first headache. Standard settings produce dark or light stripes at seams of adjacent UV-islands on lightmap at mesh junctions. Normal game, moving camera masks this. In VR standing player examines room corner closely and sees every artifact.

Solution: enable Stitch Seams in Lightmap Parameters settings, lower texel size to 0.1–0.2 for static environment meshes, and UV2 (Lightmap UV) must have sufficient padding – minimum 2 pixels on 512-atlas, 4+ pixels on 1024 and above.

Temporal flickering on ATW. If lightmap contains gradients with high-frequency details (sharp shadows from small objects), Asynchronous TimeWarp picks old frame and interpolates – light flutter appears on static surfaces. This solved by smoothing AO-radius and disabling sharp point shadows in baking.

Stereo mismatch. In VR two eyes see scene from slightly different angles. Baked specular highlights – problem: baked for one viewpoint and don't change on head shift. In VR this breaks depth perception, object seems flat. For mobile VR better not bake specular at all – only diffuse + AO.

How to properly setup baking for VR-scene

Choosing baking backend. Unity Progressive Lightmapper – standard. GPU Progressive (via OIDN denoiser) faster, but requires tuning: increase Sample Count to 512–1024 for gutter zones, enable Prioritize View for zones visible from typical player position.

Dividing into Baked and Realtime. Not all environment needs baking. Static walls, floor, ceiling, large furniture – Baked. Objects that can move or react to player – Mixed or fully Dynamic with Light Probes. Light Probe Groups placed where Dynamic objects appear: interaction zones, NPC routes.

Ambient Occlusion. In baked variant, AO – part of Indirect Lighting or separate map in Substance Painter/Marmoset. For VR recommend contact AO with small radius (0.05–0.15 m) and high intensity: gives sense of weight to objects without distance artifacts. Large AO radius in VR-room creates illusion of "dirt" on walls.

For Quest: lightmap atlas maximum 1024×1024, preferably 512×512 for most scenes. Multiple atlases better than one gigantic – simplifies streaming on zone transitions. Storage format: ASTC 6×6 via override in Texture Importer.

Baking in third-party tools

For high-quality PC VR content use Marmoset Toolbag (fast GPU baker, excellent AO with ray-traced shadows) or Substance 3D Painter (per-object baking in texture pipeline). Resulting maps imported in Unity as Emissive or blended in custom shader with realtime component.

For large scenes – Blender Cycles with denoise (Intel OIDN or OptiX) as offline baker: slower, but yields cinematic quality results for cinematic VR experiences.

Cost calculated individually after scene audit and quality requirements.