Why do objects pass through a mesh/

I have a character with arms made from a cube object that use box colliders and low poly mountains that have a mesh collider. But when the arms run into the mountains, they go straight through instead of being deflected. The mountain has a mesh collider, not convex, and each arm has a box collider and a rigidbody, no gravity and non kinematic. Can someone please explain why the box colliders dont collide with the mesh collider?

Do you mean that the arms go through the mountain? Then it’s a clipping problem. You could fix it like this:

Make A Hands Layer and set it to the hands, then you should make another camera that only renders the “Hands” Layer and make it a child of your main camera. Make sure to set the new camera to “Depth only” and make the depth 2 and set your original camera’s depth to 1 and set it to not render the “Hands” layer.

if you have any questions or you didn’t understand my answer, just ask!

Check physics settings to make sure mountain and box’s layers can collide with each-other.