GPU Rainfall

Pierre Rousseau, Vincent Jolivet et Djamchid Ghazanfarpour.
Institut XLIM - UMR CNRS no 6172 - Université de Limoges


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Outdoor video-games can improve their realism featuring weather effects. However, simulating rain can yield many problems. We hereby present solutions to address these problems, and introduce a complete framework to simulate rainfall in a video-game. Rendering uses shaders to refract the scene inside the raindrops, based on optical properties. Retinal persistence is also considered. Animation is entirely conducted on the graphics hardware, taking into account collisions and wind advection. An interface is presented, which allows the creation of complex wind-fields by the user.


These two videos use a test scene taken from the video game Secret of Time.
Day scene Night scene

Cn coefficients

cn coefficients (cn . 104) for n =
a (mm)012 345678910
0.5-28-30-83-22-3210 000
0.75-72-70-210-57 -6730-101
1.0 -134-118-385-100-5176-1-3 -11
1.25-211-180-592-1474 3210-3-5-12
1.5-297 -247-816-188245213-8-8-1 4
1.75-388-309-1042-2215375 15-15-1207
2.0-481-359 -1263-244919915-25-16210
2.25-573-401-1474-25513712111 -36-19613
2.5-665-435-1674 -2581871414-48-211117
2.75-755-465-1863-251242157-7-61 -211721
3.0-843-472-2040-240 299168-21-73-202524
3.25 -930-487-2207-222358175-37-84-16 3427
3.5-1014-492-2364-199419 178-56-93-124330
4.0-1187 -482-2650-148543171-100-107264 32
4.5-1328-403-2889-106662153 -146-111188131


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Download an archive containing all these masks.


Mapping of the catured texture onto the drops Shaders for the collision texture Shader updating the particle and position textures Shader updating the wind texture
Cg shader
Pixel shader
Cg shader
Vertex shader
Cg shader
Pixel shader
Cg shader
Vertex shader
Cg shader
Pixel shader
Cg shader
Pixel shader

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Last Modified: 06th of March 2008

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