Collision Mesh
Simplified geometry used for physics
Also known as: Collision · Simple collision · UCX · UBX · Collision hull · Collider
Definition
A collision mesh is a simplified shape that the physics engine uses in place of a model's visible geometry. In Unreal Engine, a Static Mesh can use simple collision (boxes, spheres, capsules or convex hulls) or complex collision based on its render triangles. Simple collision is far cheaper and is the normal choice. You can generate it in the editor or author it in your 3D package and import it together with the mesh.
In production
In Blender, Maya or 3ds Max, name collision shapes with Unreal's prefixes (UBX_ for boxes, UCX_ for convex hulls, USP_ for spheres, UCP_ for capsules) followed by the name of the mesh, for example UCX_SM_Barrel_01, and export them with the mesh. Keep convex hulls few and simple; UCX_ shapes must be convex. Per-triangle complex collision is for special cases such as walkable terrain, because it is much more expensive to test.
