Jinwei Gu Ravi Ramamoorthi Peter N. Belhumeur Shree K. Nayar Dirty Glass: Rendering Contamination on Transparent Surfaces. 159-170 2007 Rendering Techniques https://doi.org/10.2312/EGWR/EGSR07/159-170 conf/rt/2007 db/conf/rt/rt2007.html#GuRBN07