This was my final independent project for my undergraduate internship at Pixar during the summer of 2010. Over the course of a week and a half I developed a procedural snow generation system in Houdini as well as Render Man shaders for two different types of snow.
The procedural generation system takes as input any .FBX mesh (easily exported from Maya) and then proceeds to clump snow onto the mesh based on various heuristics and then molds the snow into drifts based on input parameters. The user can edit the system to control the amount of snow buildup, the wind direction, and the wind speed. I build a ray casting system that approximates ambient occlusion to more realistically simulate snow accumulating in appropriate locations. The snow drifting system also uses a ray casting system to simulate wind drag around objects and build up snow in areas of high turbulence and/or low velocity.