20150521 - Natalya Tatarchuk: Applied Graphics Research for Video Games
Lots of great stuff in Natalya Tatarchuk: Applied Graphics Research for
including the "Case Study: Low Res Transparency - Improved Method
General idea without optimizations,
render full resolution then down-sample depth to 1/4 x 1/4 resolution grabbing minimum and maximum.
Blend soft particles to both minimum and maximum.
During up-sample, each group of 4x4 pixels could possibly source from 4 minimum and 4 maximum samples (weighted average of 8 values).
The same method can be applied to solve transparency and MSAA blending, by blending in transparency during a custom MSAA resolve.
With GCN's layered MSAA layout it might even be possible to remove the down-sampling pre-pass.
Could grab minimum and maximum from from just the first MSAA layer.
That may miss some thin sub-pixel geometry in-front of the first MSAA layer.
In the compute custom MSAA resolve could image store if a 4x4 pixel tile misses thin sub-pixel geometry.
Then use back-projection to use that flag in the next frame to force a full check.