Barycentric centroid sampling method and apparatus

Abstract

A method and corresponding apparatus for calculating the centroid of a fragment to be rendered is disclosed. The method calls for moving the sampling point of a pixel from its initial center point to the center of the fragment containing a portion of an image to be rendered. The method comprises the steps of receiving a coverage mask containing at least one sample point of the pixel fragment under consideration; determining which of the sample points are within the fragment; determining a value representative of the number of sample points that are within the fragment; determining offset values of the fragment centroid based on the number of sample points within the fragment; and determining the barycentric coordinates of the centroid of the fragment. The centroid of the fragment is where sampling of the primitive will occur. By sampling at the centroid of the fragment, rendered image quality is improved due to the reduced anti-aliasing effects at the edges of the primitive.

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