So I have a pretty good PC. I'm getting a smooth 60 FPS in most places, at highest settings, and I have the FPS setting in Options set to cap at 60.
However, the game is frequently setting the FPS cap to 30 (as verified by my FRAPS readout in the corner of my screen). It's not so much that I'm entering an area my computer can't handle (though that may provide some input for the problem), but that the game is simply taking my framecap from 60, down to 30. Sometimes it goes back up. It seems to be largely irregular.
I don't have any resource-intensive programs running in the background. What's going on here?
EDIT: Setting all of my video settings down to Low (I typically run at highest) has no effect. I still get frequent slowdowns to a smooth 30 FPS.