r_OverBrightBits "0" - This command defines the brightness level of the map. The higher the number, the brighter the map becomes (0 being the lowest possible value). For some reason this command eats up a shit load of frames. I had it set to 16 and when I tried changing it to 0, I gained about 20-30 fps (on an AMD XP 1600+ / GeForce 3 Ti200 combo). So if you need the fps boost, set this to 0. Your game will appear extremely dark at first, but don't worry, you can brighten it up again with r_intensity and r_gamma which are explained next.
r_intensity "1.8" - This command increases the brightness of texture colors. With a low r_OverBrightBits, you may have to boost this to around 2 (default is 1). Keep experimenting until you find a brightness level you are comfortable with.
r_gamma "2" - This is the master command that adjusts the brightness level of everything in the entire game. All splash screens and menus, along with the actual game play is affected. The default value is 1, but you should usually make this higher, depending on the brightness of your monitor (and to compensate for a low r_OverBrightBits setting). Try 1.4, 1.6, 1.8, 2 etc until you find a good setting. When setting r_OverBrightBits to 0, you'll have to juggle around between r_intensity and r_gamma until you find something you are comfortable with.
r_vertexLight "1" - This is the command to enable vertex lightning. It removes many of the special effects and makes the map look somewhat dull. You should experience a decent fps boost with vertex lighting enabled.
r_picmip "3" - This is the texture detail command found in Setup / Video. The higher the number, the less detail you will have. 5 is a good value, because it blurs out the textures so you can see your enemies clearer, but if that's too much for you, try 3 or 4. The command defaults to 1 and can go up to 16. If you have simple items enabled (explained next), you'll want to set picmip to 3. Anything higher and some items become blurred beyond recognition.
r_subdivisions "80" - The higher number, the less curves there will be in the map, with values ranging from 0-80. If you need fps try 80. If you can spare some, stick with default 4 or 20.
r_texturebits "16"
r_colorbits "16"
r_depthbits "16" - Makes the color depth of the game 16 bits. Change these values to 32 for a smoother picture. If you need the fps, stick with 16.
r_lodbias "2" - This is the Geometric detail setting found in Setup/Video. Keep it at 0 if you don't like square models. 1 is default and 2 is the lowest quality (more fps).
r_fastsky "1" - When set to 1, This command disables the sky, giving you better fps.
