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So I was wondering whether or not the glass shader present within Blender is already PBR accurate. The only reason this sparks my attention is that I'm working on a watch at the moment in Blender, and I just want to ensure that the glass for the watch is PBR accurate.

Any information about this would be greatly appreciated.

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    $\begingroup$ It isn't pbr accurate. I don't know exactly why, it's because it doesn't have Fresnel built in or something. The free pbr shader at remingtongraphics.net/pbr-shader has a pretty good glass shader if you're intrested $\endgroup$
    – Linguini
    Commented Sep 4, 2017 at 22:05

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No, but you can get true PBR using the new Principled BSDF, which is available in the 2.79 RC 2 build.

To learn how to use the Principled BSDF I recommend watching this video by Blender Guru.

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    $\begingroup$ I don't understand why this was downvoted. OP asked essentially a yes/no question. I clearly answered that the Glass BSDF is not PBR accurate. I then explained that 2.79 would enable OP to achieve PBR glass, and linked to the best tutorial I know of on how to use the Principled BSDF. A downvote with no feedback doesn't help. $\endgroup$
    – Mentalist
    Commented Sep 8, 2017 at 1:30
  • $\begingroup$ The glass BSDF is not any less "PBR accurate" than the Principled BSDF. The "less accurate" complaints about other shaders vs the Principled BSDF dealt with how diffuse and glossy components were blended when roughness is non-zero. Glass does not involve this mixing, so it does not have any limitations compared to the Principled BSDF. For a simple glass surface, it really doesn't matter which of the two shaders you use. Most of the code being run under the hood is the actually the same. $\endgroup$
    – JtheNinja
    Commented Apr 13, 2018 at 6:51
  • $\begingroup$ @JtheNinja If you add any roughness to the glass you will see that there is in fact a big difference. Give it a try. Accurate calculation of roughness is required for PBR. If you're arguing that glass doesn't need roughness, I disagree. You can do an image search for "rough glass" or "frosted glass" to see all sorts of glass materials that demonstrate why roughness matters. $\endgroup$
    – Mentalist
    Commented Apr 13, 2018 at 7:59
  • $\begingroup$ I am unable to see any difference between the two shaders with any roughness value. Are you sure you used the same microfacet model (glass uses beckman instead of GGX by default) and matched the roughness value? (until recent nightlies, glass BSDF did not use squared roughness) $\endgroup$
    – JtheNinja
    Commented Apr 13, 2018 at 15:00

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