Snow Shading Kick Off

Finally, I choose to do snow shading for my final project. I like snow, it will be interesting to construct a snow white world. There are two parts in this project: snow accumulation and snow fall. After some research, I started to get some ideas for snow shading.

Snow Accumulation
Snows distribution differs for different terrains. This is determined by the height and gradient.  I need to calculate the coverage of snow of terrains: terrains may be exposed to the snow or not, heights of accumulated snow also varies. How to calculate exposure? We could transform models into ortho view from the point of sky. And then use the depth to determine whether points are occluded. For the accumulation heights, use the normals to get them. While rendering the snow, we also need some noise to make snow Glisten.

Snow Fall
http://oos.moxiecode.com/js_webgl/snowfall/
This is the result I want.
First I need a function to generate snow in a 2D plane and  give snow a random depth. Then determine the size and  blur effects due to its depth. Maybe I could also design different shapes for snow.

Hope my final project goes well!!

Reference:
http://http.download.nvidia.com/developer/SDK/Individual_Samples/DEMOS/Direct3D9/src/SnowAccumulation/Docs/SnowAccumulation.pdf
http://jimbomania.com/software/snowfall.html
http://171.67.77.70/courses/cs448-01-spring/papers/fearing.pdf