Collision mesh

A collision mesh (sometimes collision model, though it is actually only ever a component of a model) is a cheap 3D mesh used by Source to calculate VPhysics collisions.

A collision mesh is not visually represented to the player, and should be extremely low-detail compared to any reference or LOD meshes - see the images to the right for two examples. The lack of precision will not be noticed, except in that it doesn't grind the simulation to a halt!

• In order to create an accurate collision mesh for a complex concave model, you need to create several individual convex objects. If they are not separated into multiple objects, the engine will treat them as one convex mesh.
• Unlike the reference mesh, the collision mesh must be solid on all sides. Errors similar to WARNING: Model has 2-dimensional geometry (less than 0.500 inches thick on any axis)!!! mean there is a missing face somewhere.
  • This can happen if two convex objects become merged; in 3DS Max ensure you have applied at least one smoothing group before exporting.

See also

• Physics and Ragdolls
• $collisionmodel - QC command for collision meshes without moving parts
• $collisionjoints - QC command for collision meshes with moving parts