Rendering Falling Rain and Snow (sketches 0186) Niniane Wang∗ Microsoft Corporation (now at Google Inc.)

Realistic-looking rain and snow greatly enhance scenes of outdoor reality, with applications including computer games and motion pictures. We present a novel technique for realistically and effi-ciently rendering precipitation in scenes with moving camera po-sitions. We map textures onto a double cone, and translate and elongate them using hardware texture transforms. Most previous work modeled precipitation as a particle system [2], which produced realistic movement. We target real-time appli-cations that require fast performance, which is often difficult with a particle system, especially for scenes of heavy precipitation. In-verse Fourier transforms [1] have been used to render falling snow over a static background image with real-time performance. Our technique addresses the additional challenge of rendering precip-itation with a moving camera position. We also offer more fine-grained control over motion factors and drop appearance