I have a major problem and Emon suggested I post it here because ydnar is apparently very knowledgeable about these sort of issues.
I have made a huge Jedi Outcast SP level, and it’s 99% complete. Before I release it, I need to resolve performance issues. In outdoor areas in the level I am getting framerates of less than 10, and here’s why:

The building in front is sealed with structrual brushes. There is an area portal on the door but it doesn’t appear to be working correctly. Here’s an aerial shot of the area in case that helps:

This problem doesn’t just occur here though. Whenever I am outside a building, the game insists on loading near enough every triangle in the level. I can’t find any way of blocking this, it’s proving a serious threat to the release of a level that I’ve spent nigh on a year working on.

I like the colors.