Thank you very much, creasia.
but sorry, no tutorial.
just can say that,
about snowy tree, I used tree model file and push modifier applied and delete bottom polygons with ignore backfacing option.
and most of snow and raindrop material is downloaded mxm site.
I have some mistake to make this snow materials.
you can see the different of ground snow and tree snow.
tree snow is more white than ground and car snow.
ground and car snow has displacement mapping.
and used physical sky without sun + 1 emitter.
snowflakes are made with scatter and motin blured.
I first tried it with particle flow but I couldn't get the motion blured image.
so I just used scatter.
that's all. it's very simple.
