Changelog:
- Added a Virtual Ground Plane option: computes contact occlusion against an infinite floor plane directly, without needing to create or place real geometry for it.
- Includes selectable orientation (XY / XZ / YZ) and automatic or manual floor height.
- Added a Sample Distribution option (Cosine-Weighted / Uniform). Cosine-Weighted is the new default and concentrates samples near the surface normal, producing softer, more physically accurate occlusion at the same sample count.