I tried taking a screenshot of the game running in windowed mode using the
command `DISPLAY=:0 xwd -root | convert - /tmp/FILENAME`, but it only showed
the game windows as all black. Any idea why this would be?

Anyways, I just took pictures with my phone of the same door in the foyer to
the police building. The one to the outside is very dark/black and the one to
the inside (presumably the same texture and physical model) is properly
textured/lit.