Downsampling is a very different approach from polygon edge anti-aliasing and relies more on raw fillrate performance than cunning setup and sorting routines. Put very simple the accelerator renders the scene at an increased resolution and then scales it down with bi-linear or bi-cubic filtering to the end screen resolution.

The result in terms of visual output is truly amazing as you can see below, the drawback however of course lies in the fact that in order to obtain optimal image quality, the image should be rendered at twice the resolution of the final on screen image. So for 800 x 600 you should render at 1600 x 1200 for optimum results, for 1024 x 768 you should render at 2048 x 1536 and needles to say that kind of fillrate performance just isn't widely available today. The Voodoo3 3500, Matrox G400 MAX and the TNT2 Ultra are the only accelerators that could actually produce somewhat acceptable framerates at 1600 x 1200.

Of course you don't have to use twice the resolution, downscaling from 1024 x 768 to 800 x 600 or from 1280 x 1024 to 1024 x 768 is also possible, or why not 1600 x 1200 to 1024 x 768. However before we can actually reap the benefits of downsampled anti-aliasing, hardware has to support it. It has however been mentioned that Series 2 of the PowerVR architecture will support it. (See our preview).

1280 x 960 1024 x 768 800 x 600 640 x 480 (no sampling)