It does not behave differently. I see no difference with the PhysX test demo on nVidia and ATI except for the frame rate.

PhysX games normally detect the Physx speed and then reduce the number of physics objects when the speed is slow. This is just the same as with graphics, you must also adapt the graphics quality to the speed of the target system. This does not mean that graphics acceleration is nonsense and should not be used.

http://www.ogre3d.org/forums/viewtopic.php?f=1&t=59408


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there is a big difference between graphics and physics. graphics doesn't affect gameplay (at least not as much). for example... if you have to drive or run through a course of physics based obstacles or something, the game would be much easier on the cpu if there were 10 times less objects blocking your way.

Yes, thats certainly right. It would make sense not to remove important obstacles, but only remove unimportant eye candy objects when the physics is not hardware accelerated.