I've been wanting to integrate the Bullet Physics library in the real-time path tracing demo's like Tokap and Unbiased Truck Soccer for a while now (since February actually), but I lacked the programming knowledge and experience to make it work back then. Today I've finally made it work, which will open up lots of new gameplay ideas for future demo's.
I retrofitted TOKAP (the real-time path traced 3D Pong) with the Bullet physics library and the results are awesome, even though I have only tested it on a very low-end 8600M GT.
Below is a very low-res video captured in real-time on a 8600M GT at 256x256 resolution and 4spp (I will soon make a higher quality video with a GTS450):
The physics simulation can be stepped and paused by holding down the UP key. You can walk around the scene during simulation or when the simulation is paused as shown in the video. The simulation is deterministic, so it will produce the exact same result every time it runs.
Now that I've passed this hurdle, the possibilities are endless and I will finally be able to implement proper car physics (see http://raytracey.blogspot.com/2011/03/unbiased-truck-soccer-first-physics.html).
The new demo can be downloaded from http://code.google.com/p/tokap-the-once-known-as-pong/downloads/list
UPDATE: The source code is also available at http://code.google.com/p/tokap-the-once-known-as-pong/downloads/list