1 Sided Geometry, Caves ?

I’ve seen this used in many games before and I have no idea how are they made, For instance Luos Free caves pack, I want to know how are these made ?, How do they get the collision to work that good ? Thanks.

Double-click your mesh to open its properties. Under collision complexity, change the value to “Use Complex As Simple”

This works well and won’t result in a great performance lost if you keep your poly counts down.

Wow, thanks so much, didn’t think it would be as simple as changing an option.