IBL (5) specular optimize 2

FV 최적화만 추가한 건가?

예제

https://github.com/bartwronski/CSharpRenderer/blob/master/shaders/optimized-ggx.hlsl

http://filmicworlds.com/blog/optimizing-ggx-shaders-with-dotlh/

http://filmicworlds.com/blog/optimizing-ggx-update/

http://masafumi.cocolog-nifty.com/masafumis_diary/2014/05/optimizing-ggxh.html