Kinematic body collision detection bugged

Unity Engine
,
1

Hello guys,

Hope you’re all doing well!.

I would like to show you how collision detection for kinematic bodies is (not)working in Unity 2019.3.0f1 (I didn’t check any other versions so far).

Collision detection mode for moving body is set to Continuous Speculative (but Discreet is working even worse)

Here are some very short videos:

  1. Kinematic rigidbody (moved by using MovePosition in FixedUpdate) vs Static collider:
  1. Kinematic rigidbody (moved by using MovePosition in FixedUpdate) vs non Kinematic but stationary:
  1. Kinematic rigidbody (moved by using MovePosition in FixedUpdate) vs Kinematic but stationary:

As you can see by looking at above short videos, bodies are never in contact with each other but suddenly collisions are being registered and reported with some weird contact points.
Deceasing velocity of moving body or increasing fixed time step can improve this situation, but… c’mon… this is not working as intended, I’m sure about this. Also I doubt this is PhysX engine itself problem.
I would like to mention that for non kinematic (moved by physic) bodies, collisions are working very well actually.

Can some engineer from Unity take a look at this? I would be very grateful.

Thank you so much!
Konrad

2

That looks like an unexpected behavior, especially if non-kinematic bodies work as expected.

I’d recommend you to file a bug report including those scenes so the problem could be easily looked at by someone in Unity. The comparison with the non-kinematic body would be important, i.e. the same scene with a body without Gravity moved left-right by applying forces only.

1 Like
3

Hey any news on this issue? Was a bug report created?