# Chapter 23. High-Speed, Off-Screen Particles — Iain Cantlay

- Source: https://developer.nvidia.com/gpugems/gpugems3/part-iv-image-effects/chapter-23-high-speed-screen-particles
- Volume: GPU Gems 3
- Note: add-only excerpt; images omitted.

## Summary of full chapter read
Render soft/volumetric particles to fractional-resolution RT to cut overdraw. Pipeline: solids → downsample depth → particles vs small depth → composite upsample.

Depth downsample: point sample → halos; max-of-samples shrinks silhouettes (hack, looks better). Soft particles free once depths available. SeparateAlphaBlend: RGB conventional, alpha product of (1−α). Mixed-res: Sobel edges → stencil mask → full-res particles only on edges. Best for low-frequency smoke/fog; not sharp debris. 4×4 mixed ~51 FPS vs 25 full at 1600×1200 8800GTX with heavy overdraw.