visibility

Hello, I have created a brush with func_areaportal and assigned the texture to the whole brush. The brush itself is the size of the door and aligned with the wall. The problem is that I can see the void from the inside of spawn, however once I get close to the door and it opens the problem isn't...

I am having a visibility issue in one of my maps that I can't get my head around. Basically certain items in the map appear to flicker when viewed, but only from a particular location. I recorded this to help demonstrate: The spinning item you see is a func_rotating, and wall around it that...

I have various func_brush's that I am using around my map because they all receive the 'color' input at various points. My problem is that some of these brushes keep disappearing when viewed from certain points in the map. I had assumed it was a visibility issue and checked my portal file, and...

I have this building in cp_kalinka I would like to run a skybox brush through to separate the areas more. I can't however figure out a way to do it so the building would be visible from both sides of the skybox brush. Anyone got any ideas if this would be possible or if theres another way to...

This is probably an easy fix that I'm sure has been asked and solved before, but I couldn't think how to describe the problem. Basically in 2 locations of my map, I can see a room that I'm not supposed to see. These 2 areas are the same, just mirrored. But I only see this error in these 2 areas...