I encourage everyone to try this amazing new tool called Smode :
I don't know how to describe it. It's a mix between 3d modeling packages (3dsmax, maya, xsi, ...) and Compositing packages (Combustion, After effect, ...) but everything is in real time ! (OpenGL)
It's a bit hard to start but there are some good tutorials here : http://www.galago.fr/smode/doc/
here is a screenshot :
Have fun !!!