David Schedl, Michael Wimmer
Simulating partial occlusion in post-processing depth-of-field methods
In GPU Pro 4: Advanced Rendering Techniques, pages 187-200, March 2013
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David Schedl, Michael Wimmer
A layered depth-of-field method for solving partial occlusion
Journal of WSCG, 20(3):239-246, June 2012.  [
paper]