WebGPU: Volumetric Raymarching Guide
Traditional rasterization pipelines fail to simulate non-solid volumetric phenomena like dense fog, atmospheric hazes, and light shafts. WebGPU Compute Shaders and Volumetric Raymarching provide general-purpose parallel compute pipelines to evaluate participating media physics at 60 FPS.
Volumetric Raymarching Compute Pipeline
How compute workgroups integrate Beer-Lambert extinction and Henyey-Greenstein phase functions:
Compute shaders dispatch $8\times 8$ pixel tiles, casting primary rays through 3D density grids. At each ray step, Beer-Lambert transmittance $T = e^{-\sigma_t d}$ is integrated with in-scattered light modulated by the Henyey-Greenstein phase asymmetry factor $g$. Dynamic blue-noise ray jittering coupled with temporal accumulation eliminates sub-sampling artifacts.
Rendering Approaches Compared
| Pipeline Architecture | Scattering Physics | Frame Time (4K UHD) | Memory Bandwidth |
|---|---|---|---|
| WebGPU Compute Shader (Hierarchical DDA) | Full Participating Media (Anisotropic) | 2.4 ms (416 FPS) | Low (Direct Storage Buffers) |
| WebGL 2 Fragment Shader Multi-Pass | Isotropic Single Scattering | 11.8 ms (84 FPS) | High (FBO Ping-Pong Ping) |
| CPU Software Raymarching | Uncalibrated Heuristics | 142.0 ms (7 FPS) | Severe CPU-to-GPU Stalls |
WGSL Shader Engineering Invariants
Fundamental rules for writing high-throughput WebGPU compute shaders:
- Hierarchical Empty-Space Skipping: Traverse 3D hierarchical bounding volume grids (BVH) to advance rays across zero-density regions in single step evaluations.
- Half-Resolution Bilateral Upsampling: March volumetric light at $0.5\times$ screen resolution and reconstruct full resolution output using depth-aware joint bilateral filtering.
- Coalesced Workgroup Shared Memory: Load local volume density blocks into `var
` memory to maximize L1 cache hits across threads.
Engineer Modern Visual Experiences
Build next-generation interactive graphics on the open web. Review our technical guide on WebGPU Volumetric Shaders, examine Linux io_uring Zero-Copy I/O on WinWinHost, inspect V8 TurboFan IR Analysis on WebDesigner.la, or consult our GPU visualization studio.