I'm wondering if other people have experienced the low framerate of the game. For me, on a GTX 580 and AMD Phenom II X6, 8 GB RAM, and SSD, if I turn all the graphics settings to max, I get 16-17 fps. At minimum settings I usually only get around 30 fps. I know one of the biggest hits to it between those is the addition of advanced shadows, so it seems that that is not very well optimized at all, but I'm wondering if the game in general is not very well optimized as it runs so slowly to begin with. I'm probably going to play with only Complex shadows at around 25 fps, but that feels really low to me, as I'm used to 60 fps.

Any help would be appreciated.

I decided to play this game again, having forgotten about these issues I had in the past. I messed around with some settings, and apparently it was the NVidia threaded optimization that was causing the issue. I just made an override in my NVidia control panel to turn it OFF, and everything works great. Apparently DoP doesn't play nice with the AUTO setting there.

Edit: I apparently can't mark my own post as a solution, but this is the answer, at least for me. Maybe it will help someone else, so they don't need to check various video card options to see which one sticks.

Thanks for posting the solution to your slowdown problem. I checked this out and found out having this option turned on does indeed slow everything down for all of our games except our latest game, Zombasite. In Zombasite we started using VBOs, so I'm guessing that it has something to do with not using VBOs.