If you are running on less than a stellar system, and are wondering about the image quality versus performance aspect of UT3, wonder no more!
If you launch UT3, click on Settings, click on the Video tab, then click on Advanced, you will see three settings that will allow you to tweak for improved frame-rates; Screen Percentage, Texture Detail, and World Detail.
Screen Percentage will blur the screen image from the outer-edge inward. Changing this percentage to 75% will, in effect, blur the outer 25% of the screen. In doing so, your video card doesn't have to process as many high-end textures as it does at 100%. The problem with this is if the image is too blurry to see what the hell is going on around you. I wouldn't recommend dropping this setting below 70-75%. Besides, you'll have a greater performance impact adjusting the the Texture & World Details. Here is a list of their effects:
5) 16x Anisotropic Filtering is automatically applied
4 & 3) 4x Anisotropic Filtering is applied
2 & 1) Anisotropic Filtering is disabled
5) All effects and maximum detail are used.
4) Motion Blur, Quality Bloom, and High Quality Characters are disabled, and Shadow Filtering Quality is lowered.
3) additionally Dynamic Shadows are disabled, and Dynamic Lights and Particle Effects are lowered.
2) The same reduction as level 3, plus Static and Dynamic Decals, Lens Flare, and Light Environment Shadows are disabled.
1) The same reduction as level 2, plus # Dynamic Lights and SpeedTree foliage are also disabled.
In most on-line examples, images are shown with just one of the sliders being adjusted. Since it is likely that one would adjust *both* sliders to gain better performance on a lower-end system, I made a couple of animated GIFs to serve as an example. In both GIFs, I changed the settings for both World & Texture, and recorded the setting number in the upper left corner of the image. The first GIF is of a highly detailed texture (namely, the Paladin), the second is of world geometry of a map.
Dropping from 5 to 4 only gained about 3 fps, dropping from 4 to 3 gained an additional 3 fps, dropping from 3 to 2 (largest jump) gained an additional 7 fps, and dropping from 2 to 1 gained an additional 2 fps. On lower-end systems, I'd recommend a setting of 2 for both Texture & World. If you have a higher-end rig, but would like a little extra performance, 4 is almost undetectable to the human eye as 5.