Weighted, Blended Order-Independent Transparency

I'm leaving this up for historical reasons, but I recommend my more recent post on blended order-independent transparency for implementors.

Glass, smoke, water, and alpha-cutouts like foliage are important visual elements in games that are all challenging to render because they transmit light from the background. This post explains a new method called Weighted, Blended OIT for rendering all of these effects quickly and with pretty good quality on a wide set of target platforms. (As is common game developer jargon, I refer to all of these as "transparency" effects. The appendix of my earlier transparent shadow paper with Eric Enderton explains the subtle differences between them.)

The traditional approach is to sort the transparent polygons, and then render them in order from farthest from the camera to nearest to the camera. That sorting is itself slow, and causes further performance problems because it triggers more draw calls and state changes than otherwise needed and prevents common performance optimizations such as rendering amorphous surfaces like smoke at low resolution.