Front-to-Back Blending with Early Fragment Discarding

Alpha-blending is a frequently used technique implemented in graphics hardware to achieve effects like transparency, volume rendering, displaying particle systems and others. A common approach to using blending is to sort objects from the furthest to closest (back-to-front) and render them in this order. However, the inverse order can be used with some small modifications to the blending process. This paper introduces an approach to use the front-to-back rendering order to discard fragments of rendered polygons that would not influence the visual result and thus speed the rendering up. The speed gain and visual compromises are measured in several scenarios simulating practical situations and the measured results are discussed and conclusions are drawn.