mat_wireframe
... 
mat_wireframe is a console variable available in all 
Source games.
Mat_wireframe set to 1. Note the tree is being drawn by the engine even though it is behind the wall. This is an example of visibility issues.
A console variable for toggling a wire-frame mode that shows how much of the game world is being rendered.
It has four settings (0-3).
- mat_wireframe 0
- Off. Do not display any wireframes.
- mat_wireframe 1
- Displays all triangles the engine is rendering. The world brush polygons are rendered in pink.
- mat_wireframe 2
- Shows a simplified view of triangulated world brush polygons in green, using a hidden-line style rendering. Should not be used for visibility optimization since it does not accurately represent the full vis set, but can be useful for a less-cluttered display of nearby geometry in view.
- mat_wireframe 3
- Same as
mat_wireframe 1, but does not display triangulation of brush geometry. The world brush polygons are rendered in pink.
No matter what active mode, the non-world objects always use the following wireframe color codes:
- Models - Cyan
- Sprites - Green
- Displacements - Green
- Decals and Overlays - Yellow
This variable is a cheat.
