The OpenGL tab allows tuning of low level Open GL renderer settings.
Dither:
If the display is an a 16-Bit color mode, sets the frame buffer color dithering option.
Smooth textures:
Applies bilinear texture filtering so that textures are appearing smooth.
MIP-Mapping:
Applies Mip-Map filtering to textures and computes the scaled down mip-map levels for image textures
HW MIP-Map Generation:
If supported by the OpenGL driver the driver/card is computing the mip-map levels
Compress textures:
If supported by the OpenGL driver is image textures are compressed by the driver.
Use extensions:
use of Driver specific OpenGL extensions
Software rendering only:
force slow Microsoft Software OpenGL rendering
Z-Buffer depth:
the number of bits for the depth buffer: 16-Bit, 24-Bit, 32 Bit
24-Bit/32 Bit is recommended for qualtiy and avoiding depth overlap rendering
artifacts.
The status lines below are showing OpenGL Renderer information,the frame buffer configuration and supported OpenGL extensions.
The settings can be tweaked for certain scenarios, like latest ATI/NVidia cards versus older cards with limited capabilities.
Quality Settings:
Enable: Smooth textures, MIP-Mapping, HW Mip-Map Generation, Use extensions,
Z-Buffer Depth 24
Disable: Compress Textures, Software Rendering only
Also: Enable Anisotropic Filtering in the Render options tab
Anti-Aliasing : Enable Anti-Aliasing in the Display Driver Settings
Settings for low end cards:
Enable : Use extensions, Z-Buffer Depth 16
Disable: MIP-Mapping, HW Mip-Map Generation
Settings if low on video memory or cards/laptops with few video memory:
Enable : Compress Textures, Z-Buffer Depth 16
Disable: MIP-Mapping, HW Mip-Map Generation
Reduce max texture size to 512 or even 256 in the Performance tab.