mat_leafvis
mat_leafvis is a console variable available in all 
Source games.
It is a console variable that (when active) displays visleaves. The number of the leaf, area and cluster of the current leaf is reported in the console.
- mat_leafvis 0
- Off
- mat_leafvis 1
- Draw the visleaf the player is currently standing in as a red wireframe.
- mat_leafvis 2
- Draw the current viscluster the player is currently standing in as a red wireframe.
- mat_leafvis 3
- Draw all visible leaves. Note that this is unaffected by r_lockpvs.
This variable is a cheat.
