This is global set up for setting physics blend weight This does multiple things automatically If PhysicsBlendWeight == 1.f, it will enable Simulation, and if PhysicsBlendWeight == 0.f, it will disable Simulation. Also it will respect each body's setup, so if the body is fixed, it won't simulate. Vice versa So if you'd like all bodies to change manually, do not use this function, but SetAllBodiesPhysicsBlendWeight