From Dexterity.com: I have been playing around with Irrlicht and OGRE. Irrlicht seems to be much easier to use and it has collision detection. OGRE has a lot more features and you can incorporate one of the open source physics engines into it for collision detection. However, I keep wondering about the future of Torque and 3D Game Studio A6 looks pretty full featured. Altough, based on the A6 documentation, I am not convinced that it is easy to program if you don't do the scripting route. I like to hear some more success stories on the varies engines?