Node layout for glass

I have seen a number of different opinions on what light paths should be sent to the mix shader for doing archviz glass for quick renders. I've always used either just the shadow ray, or the shadow ray and the reflection. Some suggest using a combination of shadow, diffuse and glossy and I've even seen some including more beyond that.

What is the correct way and more equally important, why?

I'm putting together a general tutorial on Glass and I really want to ensure I'm giving out the optimal method here to the viewers.

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    $\begingroup$ Hello, are you planning to use Eevee or Cycles (or both) ? $\endgroup$
    – Gorgious
    May 15 '20 at 10:00
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    $\begingroup$ Hey :). Also, are you looking for the physically correct way or 'archviz glass for quick renders' you mentioned? $\endgroup$ May 15 '20 at 10:38
  • $\begingroup$ Thanks for replying, Cycles is the target here and I'd say the focus is archviz glass for quick renders but I'd want to note what is being given up for the sake of speed too. $\endgroup$ May 15 '20 at 10:53

Note: This has nothing to do with physically based glass.

Andrew Price reccomends this 'Glass Hack shader' specifically for archviz renders, where caustics aren't that important. Relevant part of video here

Working principle
It doesn't affect Shadow, Diffuse and Glossy rays in any way, but your camera still sees a reflection when looking at it.

Pros: Very fast, low noise
Cons: No refraction

enter image description here

  • $\begingroup$ Hey, thanks for responding. It's actually Andrew that I'm working on with this, I'm putting together a video for Poliigon on Glass and this setup may be the one I go with however not only do you lose the refraction but the reflections become unrealistically more pronounced. $\endgroup$ May 15 '20 at 17:25
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    $\begingroup$ Oh, that I didn't expect... :). Well, then this might be a bit out of my league... $\endgroup$ May 15 '20 at 17:29

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