Chaos sometimes can not generate contact points while two dynamic convex hulls actually collide. It results in instability in the contact behavior​ - such as jittering, inconsistent contact forces, or unexpected collision responses.

Context:
Chaos Physics is able to use convex hulls to represent object collision geometry for queries and simulation.

Problem:
Chaos sometimes can not generate contact points while two dynamic convex hulls actually collide. It results in instability in the contact behavior​ - such as jittering, inconsistent contact forces, or unexpected collision responses. This behavior is sporadic.

Suggestion:
The licensee suggests/suspects the following:
"The issue may be caused by the current strategy used for selecting the contact plane during convex-convex collision manifold construction. The current implementation of SelectContactPlane (in CollisionOneShotManifolds.cpp) selects the plane that has the closest normal alignment with the separating axis, without considering whether the selected plane actually overlaps with the other convex shape.

This can be problematic when a convex shape has multiple planes (faces) with similar or nearly parallel normals. In such cases, the current selection strategy may incorrectly pick a plane that is not truly involved in the contact, simply because its normal is closest to the separating axis.

As a result, if the selected contact plane does not actually overlap​ with the other convex, no clipped vertices will be generated during the clipping phase, and thus no valid contact points will be produced for that pair​ — even though a real collision or proximity might exist."

1.) Download and open repro project provided by licensee (Please go to case link as project is too big to be uploaded to ticket)
2.) Ensure level "StoneCollisionTest" is opened (should be opened by default when opening project), if not go to Content Drawer > Content > Developers (Settings - Show Developers Content) > StoneCollisionTest
3.) Start Play-In-Editor (PIE)​ mode
4.) Open the in-game console​ (Press `) and enter the following command: "p.Chaos.Solver.Collision.AllowManifoldUpdate 0"
5.) Move the camera​ (controlled by the player) to overlap with the trigger box located on your right side​ within the level
6.) Move the camera out of trigger box and back into the trigger box to repeat collision
Observe: The two static meshes collide: In some cases, you will notice instability in the contact behavior​ - such as jittering, inconsistent contact forces, or unexpected collision responses.
7.) Continue repeating Step 6 until observed instability or view video provided by licensee