Real-time Path Tracing of Massive Dynamic Foliage 51

Realistic open-world games demand rich natural environments with grass, shrubs, and towering trees, all subtly responding to wind. While existing methods provide practical solutions for rasterization, ray tracing still struggles: foliage requires enormous amounts of unique animation and traditional level of detail (LOD) systems are not built for ray tracing workloads. We present an end-to-end system for real-time path tracing of massive, animated foliage beyond close-range, using modern hardware-accelerated ray tracing APIs. Our pipeline combines a partitioned top-level acceleration structure with automatic clustered LOD generation and opacity micromaps (OMMs): we use OMMs to replace irreducible fine detail (twigs, needles, leaf clusters) with compact opacity masks, reducing memory footprint while preserving appearance across distances and under dynamic lighting. Together these improvements enable unique per-plant animation and LOD transitions with screen-space-bounded geometric and animation error, at the scale of tens of millions of plants.