Dave Wise pretty much covered it but I wanted to point out that I have done this before with pretty good results. Some things to point out tho are:
1. You have to key your footage and render out an .avi or quicktime animation with alpha in your nle first.
2. You have to check a setting in ambient occlusion to ignore transparency because it will affect the invisible edges otherwise.
3. The frame rate is locked at 30fps for textures in cinema and most video is 29.97 so your audio won’t sync up. I don’t know if they fixed this in later versions.
Hope this helps
Lee
Director Of Video Production (yes this is made up)
https://www.yourmusicmuse.com