Problems with physx collison

[ZZpbt.]

The method of doing deforming mesh collisions with a Face-Fractured mesh and then binding all those pieces to the original geometry is not foolproof. Depending on your deformations, it's not always possible (*usually* not possible, in fact) to maintain a 1:1 correspondence between deforming mesh face shearing levels and squash/stretch of the bound kinematic particles...so they lose parity under stress pretty quickly.

In general, the PhysX library is not that great for really tiny, detailed rigidbody setups colliding with large, deforming meshes (like a chain on a neck, as in your case). A small chain composed of actual independently colliding links colliding with a large deforming mesh is somewhat of a worst-case scenario.

You can try a couple of things:

You can skip the kinematic setup entirely and just add the deforming mesh as a Mesh collider, and increase your PhysX substeps (not the overall sim timestep). In your scene that prevented the chain from breaking. See attached.

Another thing you can do to improve your original setup, is to simply subdivide your neck collider a lot more, so the size of the kinematic faces is a lot smaller. Smaller faces means less deformations, less deformations means better collisions. You can optimize this solution by deleting all faces on the collider mesh that won't be needed for collisions, ensuring that only those faces you anticipate will collide with the chain are present in the sim. Don't forget to enable Scale bind in the Object Bind operator too. I also found that setting the Object Bind velocity mode to verlet seemed to improve stability on the kinematic particles. See attached.

Neither solution is particularly fast to simulate, but they both satisfy the criteria of chain not breaking while undergoing collider deformation.

Ok then there is no way to prevent this behaviour... None of these are solutions (mostly already tried) to prevent the collider to do those weird spikes when binded mesh surface starts to crease/fold a little too much. So you forced to arduously "clean" mesh frame by frame.
That is the only problem which breaks the chain the whole time...

Anyway, regarding the other question:
Also is there a way to prevent the collision shape to get too close to or through itself? A way to leave a gap or something like that which wont break the chain?