Idea and intent behind Principled BSDF?

I love the new BSDF shader, the way it renders things more correctly taking into account fresnel and replacing the mess with using 10 nodes to achive what should be possible with just one shader, but could not find any information on what the intent behind it is. Is this meant to replace much of all other shaders? I have not read any communication on that respect from the Blender Institute.

Or more directly asked:
Do I still need the Glass shader? Can the Principled BSDF be used for this?
I would assume that the new shader also saves on render time, as the node pipeline is not as long and since it is an integrated way of doing things.

Take a look at this response:

I don’t know about how it affects render times, but the new principled shader wasn’t meant to replace anything. It is based on the specifications for an ubershader disney developed for the production of the movie Big Hero Six.

A lot of other software and renderers support the workflow it is based on (metalness I think), so its inclusion is meant to make it easier to use textures made for other render engines. You just plug the right map into the right socket and it will work. We could do this before, but it required properly setting up a node group which requires expertise.

Anyway, the principled bsdf doesn’t have some of the other shader effects like translucency or transparent (not transmission). Also, if you want to build a unique shader like the dispersion shader, it is better to use a lot of small nodes rather than a lot of large ones.

There are going to be a few more principled shaders in the next stable (principled volume, principled hair). These are going to be useful for artists who want good results without too much setup. That is their main purpose. If you want to build odd shaders, then you’ll probably stick with the older basic ones.

Personally, I don’t really like to use the principled shader. I prefer to build my materials with the older ones. I think in the end I’ll only end up using the new principled hair shader, and maybe the principled volume.

Yes and no.
I never use the glass shader, I prefer to setup my own fresnel->refraction/glossy combo due to them sharing all the controls (color, roughness) in the glass shader. The Principled BSDF cannot be used to mimic glass as fresnel is equal on forward and back facing faces. This is very neat in most cases (i.e leaves and other simplified geometry), but not for glass.

The principled shaders are easier to use, if you don’t want to play with nodes (some people love them, some people hate them) at the cost of in-depth control.

All that being said, the principled shader can be used for basic glass, if you aren’t concerned with that level of control. It is a little brighter than the standard glass, so they certainly aren’t interchangeable:

Render times are complicated, but in general, the principled shader will be slower than other base shaders, but most likely faster than a complex node tree.

I get identical brightness for full white colored principled and glass shaders.
Was this updated or was my previous comparisons broken? Now for single plane stuff the transmission fresnel is “broken” for the backside. I cannot use incoming normal to achieve thin rough “refraction”, as the normal is shared for glossy and refraction. Basically the fresnel calculation differ for transmission. Tested this on 2.79b. Appears the Clearcoat Roughness is still broken (unmappable) as it appears to change from sharp to ggx suddenly going from 0.0177 to 0.0178.

The brightness matches at full white, but it gets worse as you go down. The reflections are affected by the color, which isn’t physically correct, and the clearcoat is indeed broken.

I’m assuming you mean the reflections on the default glass shader? Yeah, one of my pet hates about it; at the very least, we should have two colors - reflection and refraction (although I’d like different roughness control too, as well as fresnel node getting a roughness input). Reflection would normally be white but can be controlled if we want to (i.e. specular tint effects, coatings, or just to go wild). Refraction could be colored to achieve colored glass (i.e. for glass panes) effect without going into volumetrics.

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I was talking about the principled shader, but I hadn’t noticed that about the glass shader. I’ve just been coloring my glass with a volume absorption shader, so I hadn’t noticed the issue. Also, I rarely am using heavily colored glass, so it didn’t come up. It’s good to know that there are so many gotchas in the glass shader