I stumbled across a really strange rigidbody-bounce behavior that can’t possibly be intended like that.
I’ve got the following setup:
I have spheres with a rigidbody, no drag, angular drag or gravity and collision detection set to continuous dynamic as well as a physic material with static friction, dynamic friction and bounciness set to 0.5 (everything above 0 generates similar results) and both combines set to maximum.
Those spheres hit a box at a 30° angle without colliding with each other. Each sphere’s velocity is 0.01 higher than the previous one. The result is this:
I also used animation curves to graph the sphere’s speed and its angular velocity after the impact in relation to its initial speed:
So the behavior is very strange in general but at a certain speed, the spheres periodically don’t get any angular velocity at all from the impact, which makes it even weirder.
I also tried to lower the fixed timestep from 0.02 to 0.01 but that way the only thing that changes is that the “no angular velocity behavior” just starts at a lower initial speed.
And I tested using continuous speculative collision detection, but that leads to a whole different, but also very strange behavior.
I’ve put graphs to those tests into a zip file because I can only have 5 files in a post.
So my question is: What the hell is happening here?
They shouldn’t collide with each other. I put the spheres on a layer and disabled collision with the same layer in the layer collision matrix. But I made another test with more time in between the spawns, just to be sure
The interesting thing is that it doesn’t seem to matter, whhere/when the spheres are spawned, because the same speed always results in the same behavior. But I made a new test where I spawn the spheres in FixedUpdate. Just with eight different speeds this time (looping): 3.5, 3.7, 3.9, 4.1, 4.3, 4.5, 4.7 and 4.9. This also nicely shows, how inconsistent and unintuitive the bounces are, depending on the collision speed.
That’s related with the parameter “Bounce Threshold” in Project Settings > Physics. When the relative velocity of a contact is below that threshold then the object won’t bounce.
Did you find a solution for this? I don’t know the size of those balls but maybe they are small balls. If this is the case, increase the ball size to 1 might help
