So when I was poking around looking for a good free physics API I naturally found the Ageia PhysX API. I thought it was the best I had found, in terms of what it could do and how efficiantly it could do it. but it was written for C++ and the tutorials are awful (i think so anyways). I kept looking and found the XnaDevRu physics API on codeplex, but thought better of using it once I discovered that object mass function for solids was only get not set... maybe I was looking at it wrong? I also found the NewtonPhyisics API, implemented in XNA though I found the implimentation to be a little invasive, well... his implementation just wasnt my style. But it was a robust API that could handel several object efficiantly.

After more searching I discovered that someone had written a C# wrapper for Ageia's PhysX API. though when I try to use some of his later demos I get a protected memory read error...

setting that aside, not all of his demos crash (;p) which leads me to beleive that the wrapper itself can still be used.

This isnt really a question I just wanted to point out some of the XNA compatible 3D physics APIs that I have found.

Although I do wonder what will happen if you try and use any of them on a 360... hmmm...

Links:

http://www.zelsnack.com/jason/JttZ/Novodex_NET_Wrapper/

http://www.codeplex.com/Wiki/View.aspx?ProjectName=xnadevru&title=XNA%20Physics%20API%20(XPA)

... and I cant seem to re-find the newton physics for XNA... oh wellz

I have to imagine they are, after all the game engine company Emergant Game Technologies is selling a game engine for XBLA games that takes advantage of Ageia PhysX...

My guess would be that if your writing a professional XBLA game the only restriction is the size, and possibly content (Mortal Kombat anyone?)

Madbarron:

To get PhysX on the 360 you would have to license it from Nvidia for a steep $50 grand. The libraries don't exist on the 360, so you purchase the right to the source and compile it with your game.
http://developer.nvidia.com/object/physx.html