[maccard]

> Typically in game engines you need to pause the world and look into the physx simulation to get the object's pos/vel/mass. This causes the physx engine to stop the world to finish it's calculations so crossing the PCI bus becomes more and more expensive.

PhysX keeps two copies of the simulation, you read from one while PhysX is updating the other, and then they swap the pointers. You don't cross the PCI bus to get every position/velocity, that info is transferred in bulk at every step.