about geometry&fresnel factor in physically based shading

Discussion in 'Rendering Technology and APIs' started by ccanan, Sep 26, 2011.

  1. ccanan

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    Hi, just did some implementation on physically based shading, read some documents, mainly from siggraph course(10's physically based shading course, 11's physically based lighting in cod_bo).
    well, I was a little puzzled: to me, phong to blinn phong, the changes are obvious.
    As the specular looks better.

    But with fresnel term and geometry term(or ā€¯visibility term" called in cod's presentation), I did find it different, but failed to find it better.
    The graphics of the engine with fresnel&geometry term just looks as good as without it.

    Sure, with fresnel&geometry term, it's correct in theory, but we dev game for gamers who don't care the theory.

    So what u think?I hope it's because I didn't assign the correct or good parameter, the programming side should have no problem.
    //-------------------------------------
    hmmm, i can't delete my post, well, now, after more reading, especially on tri-ace's ppt, get much more.
    fresnel and visibility terms are pretty useful.
     
    #1 ccanan, Sep 26, 2011
    Last edited by a moderator: Sep 26, 2011
  2. MJP

    MJP
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    One thing about physically-based shading that might not be immediately obvious is that it's not just a switch you flip that automatically makes everything look better. Really the biggest benefit (IMO) and the reason it became popular in CG/VFX industries is because it makes it easier for artists to author the material response they want. A lot of times artists will have a vision in their head based on a physically-correct response, and with an ad-hoc shading model they will spend hours trying (and often failing) to get that same response in the game. Or they might get it right under one particular lighting environment + viewing conditions, and then it doesn't work somewhere else. With physically-based shading you try to always do the "right thing" from a physical point of view, which tends to give the artist a much better starting point.

    Another thing to keep in mind is that if you drastically change your BRDF, you're probably going to need to retune most (or all) of your materials to get the most out of it.
     
  3. ccanan

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    hey, thx for that
     
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