1. A graphics system comprising: a sample buffer; a rendering unit coupled to the sample buffer and configured to receive graphics data including three vertices defining a triangle, wherein the rendering unit is further configured to (a) determine boundary coordinates for a group of bins which contain the triangle, (b) compute relative x and y coordinates for each of the vertices of the triangle with respect to an origin of said group, (c) filter sample positions in one or more of the bins of said group to determine interior sample positions which reside inside the triangle, (d) interpolate sample ordinate values for the interior sample positions based on the relative x and y coordinates of the vertices and vertex ordinate values corresponding to the vertices, (e) store the sample ordinate values to the sample buffer; a sample-to-pixel calculation unit configured to filter said sample ordinate values to determine a pixel value, wherein the pixel value is usable to generate part of a display image.