Ground contact is a screen-space signal.

Ground Truth Ambient Occlusion estimates how much nearby geometry blocks ambient light. This lab keeps the noisy AO buffer visible so the MRT inputs, sample budget, resolution scale, and temporal resolve remain measurable instead of disappearing inside a preset.

GTAO is WebGPU-only here; WebGL2 remains available as a direct baseline. Transparent materials are excluded from the built-in AO context.