Trilinear Filtering

Trilinear Filtering

Mip mapping solves the depth aliasing artifacts, but it also introduces a new artifact called "mip banding." Mip banding occurs in the LOD transitions where different sized mipmaps of the same texture border each other. The transition between different sized mipmaps isn't very smooth and most people are able to notice the areas where the mip levels shift. Mip banding is most noticeable on floors and walls because they tend to extend through several levels of detail.

Trilinear filtering manages to smoothly blend the transition from one mip level to the next. It's a combination of bilinear filtering and mip mapping. Trilinear filtering uses bilinear filtering to sample pixels from the two closest mipmap levels to determine the pixel's color, making the transition between mipmap levels very smooth. Trilinear filtering takes samples twice as many pixels as bilinear filtering, and many 3D accelerators will need to take a second rendering pass if trilinear filtering is enabled.

Trilinear filtering