Adrena Old School
Using jittered sub-pixel sample positions reduces the likelihood that a small primitive or fragment will be lost. Furthermore, the human perception system is tuned to detect regular patterns, appearing as aliasing and other artifacts. Jittering removes the regularity from a sampling pattern such as the pattern shown in FIG. 2A resulting in an image with reduced aliasing. Sub-pixel offset values to produce an irregular jittered sub-pixel sample position pattern may be programmed for use by Rasterizer 150 during scan conversion and coverage mask generation. However when a single jittered subpixel pattern is used for every pixel, aliasing will appear due to a perceived pattern. Therefore, a jitter pattern should vary from pixel to pixel, i.e. have a greater period, to effectively reduce aliasing.