Is there a way to activate an object's physics simulation only at a specific event - like a collision with another (physics) object?
Small example use-case: A cube is constantly rotating in space around it's own z-axis (animated by keyframes) but otherwise completely stationary. The cube is not influenced by gravity or any other physics yet. Then there is a rigid body sphere thrown at the cube. In the very moment when the sphere hits the cube they both should react according to the physics simulation: they bounce off each other and both get dragged downwards by gravity. (The actual scene contains tens or even hundreds of these objects - so keyframing each collision is not a good option.)
It's a scene for an animation, so I am not using the game engine.