Native bindings to the ARB_texture_filter_anisotropic extension.

Texture mapping using OpenGL's existing mipmap texture filtering modes assumes that the projection of the pixel filter footprint into texture space is a square (ie, isotropic). In practice however, the footprint may be long and narrow (ie, anisotropic). Consequently, mipmap filtering severely blurs images on surfaces angled obliquely away from the viewer.

Several approaches exist for improving texture sampling by accounting for the anisotropic nature of the pixel filter footprint into texture space. This extension provides a general mechanism for supporting anisotropic texturing filtering schemes without specifying a particular formulation of anisotropic filtering.

The extension permits the OpenGL application to specify on a per-texture or -sampler object basis the maximum degree of anisotropy to account for in texture filtering.

Increasing the maximum degree of anisotropy may improve texture filtering, but may also significantly reduce the implementation's texture filtering rate. Implementations are free to clamp the specified degree of anisotropy to the implementation's maximum supported degree of anisotropy.

A sampler or texture's maximum degree of anisotropy is specified independently from its minification and magnification filter (as opposed to being supported as an entirely new filtering mode). Implementations are free to use the specified minification and magnification filter to select a particular anisotropic texture filtering scheme. For example, a NEAREST filter with a maximum degree of anisotropy of two could be treated as a 2-tap filter that accounts for the direction of anisotropy. Implementations are also permitted to ignore the minification or magnification filter and implement the highest quality of anisotropic filtering possible.

Applications seeking the highest quality anisotropic filtering available are advised to request a LINEAR_MIPMAP_LINEAR minification filter, a LINEAR magnification filter, and a large maximum degree of anisotropy.

Requires OpenGL 1.2.