Why is there no such thing as a collider inside, but it is?

Question

Unity

Tipo shows that the collider is only on the walls, but it turns out that the whole tunnel is generally considered a collider. Like I'm trying to create a cube inside, but it pushes it out.

Answer 1

I think you are using a mesh collider with a convex checkbox. Convex translates as convex. Mesh collider does not know how to non-convex. If you want a non-convex one, then you need a composite collider. Child empty objects with colliders are nested in the object, creating the desired shape and they behave as a single whole. This way you can get the desired result.