Enabling eMODIFY_CONTACTS causes jitter on wall collision.

[kujukuju]

Library and Version

Physx 5.1.0

Operating System

Windows 11

Steps to Trigger Behavior

1. Set up a scene with a wall
2. Create a dynamic rigid body
3. Enable the scene flag eMODIFY_CONTACTS (you don't actually have to modify anything)
4. Apply a CHANGE_VELOCITY force to steadily move your dynamic rigid body into the wall
5. See the jittering effect

Expected Behavior

I expect the dynamic rigid body to not be jittery. When you disable eMODIFY_CONTACTS it's smooth.

Actual Behavior

Jittery when colliding with walls.

---

I'm trying to manually manipulate some contacts in my game, so I've set up a contact modify callback and enabled the eMODIFY_CONTACTS scene flag. I'm using the rust version of physx which is 5.1.

For reference, I am able to modify contacts and things work as expected.

However, when I enable modify contacts all collisions in my scene where I push up against a wall begin to jitter. This happens even when I do completely nothing in my PxContactModifyCallback.

I couldn't find another reported issue on this github about this. From what I can tell, it's because modifying contacts causes the physics engine to generate new patches.

It seems like this is an existing issue, because I found this user on a forum who reported my exact issue. https://gamedev.net/forums/topic/715265-physx-rigidbody-jitters-if-pushed-into-corners-depenetration-issue/

He ended up just disabling contact modification and stopped there. So unfortunately not helpful for me.

I actually went into the source code and commented out the area where it seems to force a patch update when contacts are modified and this did nothing. I wanted to go through all the source code step by step and find exactly where the bug was being caused but I actually couldn't find anywhere eMODIFY_CONTACTS was used to perform additional steps that seemed to affect the jitter bug at all.

However, I can confirm as shown in my video, as with the gamedev.dev guy, the bug only happens when the contact modification flag is enabled. Nothing else matters at all.

Here is a video showing the bug. I have eMODIFY_CONTACTS enabled at the start (with no actual contact modification happening at all), and once it's disabled the bug goes away.

https://github.com/NVIDIA-Omniverse/PhysX/assets/5142257/2b594934-bc01-4b32-8a20-da560845b287

Thanks!