pdf: http://wwwcg.in.tum.de/fileadmin/user_upload/Lehrstuehle/Lehrstuhl_XV/Research/Publications/2014/FluidRendering/paper.pdf

My most favorite visual artwork.

http://patapom.com/topics/WebGL/BRDF/

http://imgur.com/a/zxUXQ

http://www.chrisevans3d.com/pub_blog/moving-physically-based-shading/