A collision hull (also known as a collision mesh or simply hull) is a simplified version of your model that is used for collision detection. By being a simplified version of the model, it saves the game engine all the effort of detecting collisions on complex shapes.

Things To Know

1. Collision hulls must be Convex.
2. If your model is complex and cannot be realistically wrapped in a single convex shape, then the hull must be separate convex pieces.
   
3. If your hull is composed of multiple pieces, and each piece is an Element sub-object of a single mesh, then each element must have a unique smoothing group (that other elements in the hull do not share).
4. For multi-part hulls, your model QC file must have the $concave parameter.

Making a Collision Model

This page details making a hull using Wall Worm Model Tools and the Quick Hull feature.

1. For each segment of the model that needs a hull, Detach it into its own element (or object*)
2. Assign your mesh(es) to a WWMT Helper
3. Press the Quick Hull button
4. The $concave flag is automatically set
5. Each Element of each mesh in your model will get a hull made from it
6. Each hull will get a unique smoothing group
7. All hulls are automatically assigned as hulls in the WWMT Helper

• *Any piece of the model that is broken into a separate Object (as opposed to Element) with the Editable Poly Detach function is no longer part of the model and must be re-assigned to the WWMT helper with the Add Sel or Append functions before the Quick Hull Function is run.
• If your model is animated, you will need to skin the hull.
• Also see Hull Helper.

WWMT Collision Hull Utilities & Techniques

If you do not have Convexity and access to the Quick Hull button, you still have several tools in WWMT to optimize the process of making a hull.

Auto Hull

If your model is simple, you can tell the Valve model compiler to generate a hull by clicking the Auto Hull button in the Collision Model & Physics Rollout.

This function does not work in conjunction with $concave.

This function does not work with animated models.

Prepare CM

This function lets you choose a mesh and apply proper smoothing groups and textures. Read More.

Process CM

This function will apply proper smoothing groups to all hulls assigned to the current WWMT helper and give a texture. Read More.