Examples of GLQuake's texture filtering options

Different gl_texturemode settings with and without anisotropic filtering enabled in the graphics drivers (some engines have a gl_texture_anisotropy cvar for that).

Open the linked full-sized images in tabs and cycle between them to see the differences. Keep in mind that these are static images and that things appear different in motion (moving patterns in the distance and similar effects).

Bilinear filtering with no anisotropic filtering (default)

From left to right it is GL_LINEAR, GL_LINEAR_MIPMAP_NEAREST, GL_LINEAR_MIPMAP_LINEAR

Bilinear filtering with 16x anisotropic filtering

Nearest neighbor filtering with no anisotropic filtering

From left to right it is GL_NEAREST, GL_NEAREST_MIPMAP_NEAREST, GL_NEAREST_MIPMAP_LINEAR

Nearest neighbor filtering with 16x anisotropic filtering