Deferred Shading for Order-Independent Transparency

Abstract

Rendering many layers of transparency presents difficult challenges with respect to performance. Most previous work focused on the sorting problem, paying the full shading cost for all fragments. We present a method that defers shading until fragments can be classified as less important to the final pixel color, allowing us to switch to a lower-cost, approximate shading function. We apply this idea to TressFX, which is a state-of-the-art hair rendering technique used in video game production. For hair rendering, we switched to low-quality shading in all but the front eight fragments per pixel. This gave us a 75% speedup without noticeable loss in visual quality.