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[SOLVED] Area Light, Representative Point, Blinn-Phong


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#1 n00body   Members   -  Reputation: 293

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Posted 26 August 2014 - 08:10 PM

Background

Okay, so I have seen Epic's paper that covers, among other things, how they did area lights in UE4 by the "representative point" method:
http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf

 

Problem

They specifically talk about how they needed to come up with a modification to the normalization factor for their BRDF to make the intensity looks close to correct. However, the one they list is for GGX, and I am using Normalized Blinn Phong. Sadly, I don't understand the math behind normalization.

 

Question

Is there a nice simple way for me to find the normalization factor to use Normalized Blinn Phong with this area light trick?

 

Thanks. 



[Hardware:] Windows 7, Nvidia Geforce GT 440, AMD Athlon II X4 620, 6GB RAM

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#2 n00body   Members   -  Reputation: 293

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Posted 07 September 2014 - 01:05 PM

Okay, I've sort of solved it myself. Basically, I found a way to apply Beckmann roughness to Blinn Phong. This modifies the normalization term to be the way the Epic described in their paper for GGX, so I suspect the same trick they used should now apply. For anyone who is interested, here is where I found my answer:
http://graphicrants.blogspot.com/2013/08/specular-brdf-reference.html



[Hardware:] Windows 7, Nvidia Geforce GT 440, AMD Athlon II X4 620, 6GB RAM

[Websites:] Development Blog | LinkedIn
[Unity3D :] Alloy Physical Shader Framework | Free RNM Shaders





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