- Imported an fbx
- Added mesh collider to it
- Created a prefab from it
- Added it as a detail mesh to my terrain
- Doesn't collide. The prefab itself collides of course.
Collision detection is not supported for detail meshes.
Add a rigidbody to your GameObject. If that doesn't work correctly try adding a basic box collider around your mesh to see if that works.
If you want your mesh to collide with fast moving objects change the collision detection to continuous dynamic, and if that still doesn't collide correctly try increasing the FixedTimeStemp value in your projects Physics properties.