Adaptive Transparency

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 wide range 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.

Slides: AdaptiveTransparency GDC presentation [PDF 1.45MB]
Code: AdaptiveTransparency_Source.zip [29.9MB]

aoit_left_small.jpg aoit_right_small.jpg

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.

This software is subject to the U.S. Export Administration Regulations and other U.S. law, and may not be exported or re-exported to certain countries (Cuba, Iran, North Korea, Sudan, and Syria) or to persons or entities prohibited from receiving U.S. exports (including Denied Parties, Specially Designated Nationals, and entities on the Bureau of Export Administration Entity List or involved with missile technology or nuclear, chemical or biological weapons).

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