Adaptive Order Independent Transparency: A Fast and Practical Approach to Rendering Transparent Geometry
By Marco Salvi, Jefferson Montgomery, and Aaron Lefohn
We introduce a new technique for real-time order independent transparency called Adaptive Transparency (AT) that closely approximates the ground-truth results obtained from A-buffer compositing but is 5x to 40x faster. The key contribution of Adaptive Transparency is the introduction of an adaptively compressed visibility representation that can be efficiently constructed and queried during rendering. It can be applied to a widerange of transparent geometry (e.g., foliage, windows, hair, and smoke). AT closely matches the ground-truth A-buffer solution and is both higher quality and faster than other approximate OIT techniques.
Citation: Marco Salvi, Jefferson Montgomery and Aaron Lefohn. Adaptive Order Independent Transparency: A Fast and Practical Approach to Rendering Transparent Geometry , Game Developers Conference, March 2011.
Transparency is a fundamental open problem in real-time rendering due to the difficulty of compositing in the right order an arbitrary number of transparent layers. The current situation in real-time applications is exemplified by the left image, where numerous objects are incorrectly composited when rendered with alpha-blending, the most popular algorithm for rendering transparent geometry. On the other hand, as shown by the right image, our algorithm can correctly composite all transparent layers while maintaining performance levels typical of real-time applications.