What is causing artifacting in my level?

Hi,

I’ve got some weird artefacting on some of my scene geo. At first, I thought it was something to do with shadow bias, but changing the values on the affecting lights doesn’t seem to make any difference.

http://puu.sh/8jZKh.jpg

The banding changes based on the camera depth, and is very distracting. It doesn’t appear to change with AO settings.

Any ideas?