I've just added a page about fixing some anomalies and also increasing shadow resolution in the game, if anyone is having issues:
http://forums.techpowerup.com/showthread.php?t=74160
Try Full Dynamic(the one under DX10) with all the sliders full, all the sun ray, ssao and sun quality to low(with them on high it makes no diff quality wise and helps FPS alot!) no aniositropic filters and no AA(unless you want it) the grass density bar to none(makes the sprites bigger, whoopdy doo.. still looks ugly), and get this mod
I have to disagree here slightly. While for Vista users, you might as well use DX10, some sliders should not be at full, as they make little or very little difference to IQ and yet cost a noticeable amount of performance.
Check the two pictures below, to set your visuals appropriatley.
Here, distance detail is set to two clicks over, as there's not often a moment in the game where you can see beyond that (if there is, it's less than 5% of your play time and if it really bothers you, move it up one notch), and you're just throwing away frames for nothing. The same is true of lighting distance although the degredation of performance is not near as bad. The next big one, is as Shadow mentioned, sun related, but it's the Sun Rays you, which should be no higher than "medium."
Grass density, user preference, though performance doesn't seem to go either way too much.
You can ignore the AntiAliasing in DX10. So set it to 0.
Also, you don't have to use Vsync.
There's not really any configuration files(like with Crysis), that will make or break performance. Most of them are more about image preference as well as possibly sorting out some kinks or glitches.
http://forums.techpowerup.com/showpost.php?p=1003105&postcount=170
adds sunrays to game for all day instead of just 6:00AM to 8:00AM!
It seems rather silly to suggest he get a mod that causes sun rays to be more persistent, when A) He's looking to increase performance, something which you suggest in B) To turn the quality down
??
Lastly, don't forget the dual/quad core affinity trick.
When the game is running, (best to use a FPS counter the first time you do it, to make sure..)Alt-tab or CTRL ALT DEL> Bring up TaskManger. Scroll down to the XrEngine.exe and right click to bring up it's menu. Select "affinity." Uncheck all boxes except "Core 0." Do not close the Task Manager. Alt-tab back into the game, check your fps, it should rise ever so slightly(maybe for some it wont). Alt-tab or CTRL ALT DELT again, and return to the affinity menu for the XrEngine. Now tick all your remaining cores. Close Task Manager, and Alt-tab into the game. Your fps should rise by a few, sometimes several or higher depending on the in game situation area.
This DOES work, but it doesn't ALWAYS work the first time. Sometimes I have to do it twice in a row;
It's definatley worth it though