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#ActualCryZe

Posted 10 February 2013 - 04:22 PM

The only difference between mine and your GGX, is that I'm using the Walter GGX geometric term which is specifically calculated using Smith's "blackbox" function to convert any distribution function into a perfectly matching geometric term. The thing is, that the cook torrance geometric term is more or less completely absurd and unrealistic, because the shadowing and masking should be dependent on the microfacet distribution, but the cook torrance geometric term completely ignores that. That's why you get that unrealistic cut at 45 degrees. I'd recommend you take a look at Naty Hoffmann's presentation and Disney's presentation at http://blog.selfshadow.com/publications/s2012-shading-course/. You should also check out Disney's BRDF Explorer and the MERL database. With the BRDF explorer, you can validate how well your BRDF matches actual materials from the MERL database. 

 

Also, your GGX is the correctly normalized version ;)


#1CryZe

Posted 10 February 2013 - 04:21 PM

The only difference between mine and your GGX, is that I'm using the Walter GGX geometric term which is specifically calculated using Smith's "blackbox" function to convert any distribution function into a perfectly matching geometric term. The thing is, that the cook torrance geometric term is more or less completely absurd and unrealistic, because the shadowing and masking should be dependent on the microfacet distribution, but the cook torrance geometric term completely ignores that. That's why you get that unrealistic cut at 45 degrees. I'd recommend you take a look at Naty Hoffmann's presentation and Disney's presentation at http://blog.selfshadow.com/publications/s2012-shading-course/. You should also check out Disney's BRDF Explorer and the MERL database. With the BRDF explorer, you can validate how good your BRDF matches actual materials from the MERL database. 

 

Also, your GGX is the correctly normalized version ;)


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