Method and system for texture mapping images with anisotropic filtering

A method for texture mapping a source image to a destination image where a mapping of points from the destination image to the source image is described by an inverse transform, comprising:

• deriving a line of anisotropy using the inverse transform;
• computing a weighted sum of texel values from the source image sampled along the line of anisotropy, wherein scale factors used to compute the weighted sum are selected for each pixel location depending on a degree of anisotropy calculated from a change in texture coordinates with respect to view space coordinates at the pixel location;
• applying a reconstruction filter along the line of anisotropy to sample texel values from the source image and produce output values;
• processing the output values to compute a pixel value for the destination image, including applying a resampling filter to the output values and summing outputs of the resampling filter to compute the pixel value for the destination image, wherein the resampling filter scales the output values with the scale factors selected based on the degree of anisotropy.

A system for performing texture mapping of a texture to surfaces of geometric primitives, the system comprising:

• texture memory;
• a set-up processor for receiving commands and the geometric primitives, for parsing the commands, for computing inverse transform data from the geometric primitives, for computing texture addresses from the geometric primitives, and for retrieving texture data into the texture memory corresponding to the texture addresses;
• and
• a texture filter engine in communication with the set-up processor and the texture memory for receiving the inverse transform data and the texture addresses and computing a line of anisotropy through a point mapped into the texture and a ratio of anisotropy based on the inverse transform data, the texture filter engine including a first filter for sampling and blending two or more samples from the texture at a selected level of detail at each of a series of steps along the line of anisotropy to compute intermediate texel values and a second filter for computing a weighted sum of the intermediate texel values sampled along the line of anisotropy;
• wherein the first filter includes an interpolating filter for sampling texel samples from the texture at each of the steps along the line of anisotropy and the second filter includes a one dimensional digital filter applied to outputs of the interpolating filter and the digital filter uses scale factors selected based on the ratio of anisotropy.