how to make a winter image

[duke2]

I tried something like this one time and I found another good way of doing it. With the vrayextratex element, give it a composite map with:
-falloff map in the Z (snow on tops)
-falloff map set to shadow/light, tweak so it just gets the shadows, set it to multiply, ~70%

Additionally, have a GlobalIllumination element, and in photoshop, stick that at the top, and ues the result of the extratex to mask it out.

[Undersky]

Looks good, but I'd try and bring some more blue into the shadows. Since snow is white it picks up the illumination from the sky very well. Take a look at these images:



Also, you have some alpha problem with your tree on the left (clearly visible in the not-so-blue-shadow =)