Some objects fall through mesh terrain randomly

Unity Engine
1

Hi!

I was wondering if there are ways to improve mesh collision accuracy.

I have imported mesh as a terrain, which is a square about 3000m in lenght (I am using real world scales). The terrain has mesh collider enabled. However, sometimes, seemingly randomly other rigidbody objects fall through the terrain. Even in very slow velocities, like from 1m drop to the ground.

Here are some things I have noticed:

  1. Smaller objects fall through more likely than larger
  2. Objects with convex mesh colliders or rather flat box colliders fall through most often
  3. Objects with capsule or sphere colliders go through very rarely

There seems to be no change in this behavior whether I am close to the origo (0,0,0) or far from it. For performance reasons I can’t use “continuous collision” in the rigidbodies, while it could probably solve some of this. My physics time scale is 0.02, and increasing it didn’t make any change. Of course I can’t make the terrain collider out of primitives because the scale and shaping.

What suggestions do you have to improve the collision accuracy, or hopefully get it bullet proof? I am thinking of splitting the single terrain mesh into smaller pieces, but I cant do that until the actual terrain is finished. I don’t also know if that makes any difference collision wise.

2

Thats because of the speed, that these objects travels, if the speed is enough for the object to partially pass trough that object, than it can get trough, that’s why smaller objects go trough them easily.