ahhh the wonderful world of matting and keying
you can take different layers of images (reflection, diffuse, ambient, shadow etc) and put them ontop of each other and it would create the final image/animation, this is called layering and matting i believe
its like with a green screen in films, you have a character on greenscreen, and you want to put that character into a CG environment, easy. Take the live action plate, key (removing but keyframed cos its an animation) out the green put this live layer ONTOP of a layer which has your backdrop and there we go all the green is removed to show just the character jumping about on a CG background