Hi there, following on from another thread that talks about the occluder texture, I thought I would put an example in a small test map to get some screen shots to show you how well the texture can block objects from being rendered.
Here is a simple wall with occluder on the center brush x 6 sides, then either side of this brush is a 2 grid wide wall with nodraw x 5 sides and a tree line texture on the face.
Here is the same view showing how objects behind are still rendered by the engine if no occluder
And again the same view with the occluder wall inside.
I was able to walk through the wall and noticed dramatic fps jump due to sudden appearance of objects to be drawn, so I reccomend using a clip on the wall as well to block players and vehicles from going through it.