Mesh vs mesh: bumpy internal mesh's edge collision (Unity engine Physx 2.8.3)


I used Unity game engine which incorporated PhysX 2.8.3 for physics car simulation.

I use a mesh with shape similar to a cylinder to simulate wheel, and the road is another mesh. This method is better than ray casting and other shape, e.g sphere in simulate wheel’s shape.

But there is a problem, no matter what shape I used for the wheel (triangles mesh, sphere collider, cube,…), sometimes randomly the wheel bumps up on non planar road even the road is quite smooth. Only ray casting avoids this problem. But using approximate mesh for the wheel is very good, much more accurate than ray casting.

I did some researches and it seems that the wheel collider (mesh, sphere, cube,…) collides with internal edge of the road and cause bumpy effect. In bullet physics engine, they have a solution: mark all internal mesh edges and avoid collide with it.

I know this version of Physx is old (2.8.3), Unity team is planning update physx version. So the question here is that, can I hope for a fix of this problem in later version of physx? Which version should it be, so I can have some voices to suggest Unity team.

If physx doesn’t have this feature, would its team consider implement it in the future?



Since you’re using PhysX 2.8 I would suggest that you use the built in wheelshapes, from my tests they are the most stable approach. I also suggest that you only use them for collision and spring effect and apply forces to the rigibody instead since it’s easier to tweak acceleration and speed that way.

Note, that there is and issue with wheelshapes against dynamic objects. So I suggest that you build a collision mesh around the wheels that doesn’t collide with the ground but pushes away small dynamic objects.