How can I render 3d graphics on top of a live webcam feed?
Visual Studio 2008 c++
Edit:
I left the question vague because I do not care what libraries or frameworks are used. I don't care if its Direct3D or OpenGL, or even something else.
To bring it the question to a specific point, I would like to render a flat shaded spinning cube on top of a web cam feed.
One way is to use DirectX to render video on dynamic texture and render some additional graphics over it. Maybe one of these samples will help you.
You maybe want to make your question to be more specific so we could give you more specific answer.
Your question is infinitely vague (but oddly specific about your development environment), but I believe what you're looking for is called Augmented Reality.
The Wikipedia Article has a ton of good information on this, as well as links to various excellent libraries for it.
If you could provide us with more details, we could possibly help you decide which toolset to use.