Ref'd in the submission - Kroes T, Post FH, Botha CP. Exposure render: an interactive photo-realistic volume rendering framework. PLoS One. 2012;7(7):e38586. doi: 10.1371/journal.pone.0038586. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3388083/)
Generously there is also code available (last commit 2013), although I haven't tried it yet... https://code.google.com/archive/p/exposure-render/
I was curious about any overlap with an earlier post today "How Voxels Became ‘The Next Big Thing’" [https://news.ycombinator.com/item?id=17169209]