I'd like to render a 3D explosion in 3DS Max but into a sprite sheet. My main problem is that I need to use alpha values instead of the viewport background (which is usually black).
Any ideas how I could do this?
Just render to png/tga images and make sure alpha is enabled. You can enable alpha by just rendering any frame, press save and pick PNG or TGA and check the alpha checkbox. This will remembered when you render out multiple frames.