Graphics texture mapping

Sampling a texture using anisotropic filtering by: for a sampling position in a texture, comprising two or more mipmaps, the sampling position having coordinates x and y; determining the square root of coefficient F for an ellipse defined by the equation Ax2 + Bxy + Cy2 = F, the ellipse corresponding to the projection of the sampling position on to the surface to which the texture is to be applied; using a log2 operation on the square root of F to calculate an unclamped level of detail (LOD), and selecting the greater of a clamped LOD and the unclamped LOD as the LOD at which to sample the texture; using the LOD to select one or more of the mipmaps; taking samples for positions along an anisotropy direction in the mipmaps; using the samples to determine a sampled texture value for the sampling position. X and Y components of a vector corresponding to the major axis of the elliptical projection of the sampling position may be determined. The vector components may be normalised to provide X and Y components for a corresponding unit vector. The unit vector components may be used to determine the anisotropy direction.