I use OpenGL
In your system folder in your UT2004 main directory or where you installed it, there's a file there called UT2004.ini
to change to OpenGL open the file in say Notepad++ and on line 21 or
[Engine.Engine]
RenderDevice=OpenGLDrv.OpenGLRenderDevice
;RenderDevice=D3D9Drv.D3D9RenderDevice
;RenderDevice=Engine.NullRenderDevice
;RenderDevice=OpenGLDrv.OpenGLRenderDevice
;RenderDevice=PixoDrv.PixoRenderDevice
Change it from D3D9 to OpenGL as above
For Resolution look under
[WinDrv.WindowsClient]
WindowedViewportX=768
WindowedViewportY=1024
FullscreenViewportX=1920
FullscreenViewportY=1080
MenuViewportX=1920
MenuViewportY=1080
Windowed is if you play in a window
Full Screen is Full screen gaming
MenuView is the main menu since you could play ut2004 in a really low resolution so the main menu and game resolution are separate
I set them to 1920*1080
for FOV at a resolution, I set it to 106.26 deg
you can do that in game in console just hit the ~ tilde key and type /fov 106.26
