These are some simple examples of the new Principled BSDF node using the Cycles Surface root node and Superfly. Before I start - this is not a tutorial. I’m not trying to say that the way I do things is the best way, or the only way. This is just a collection of things I have learnt which have been useful to me - I don't consider myself an expert and am more than capable of making mistakes. Therefore I'd suggest doing your own tests and research - good sources of information I've used include the Blender documentation, the excellent pdf’s covering PBR theory and practice at the Marmoset Toolbag website under Advanced Tutorials, and those on Allegorithmic’s Substance Academy website.

The renders are saved from Poser as jpg's with no post processing. With each example I’ve indicated where I’ve made any changes to lights or render settings. My units are set to meters. As there is no Preview when using Cycles nodes I tend to turn on Progressive Refinement in the render settings and use a small size e.g. 600 pixels square to get quick test renders. The props are mainly simple ones to try to focus on the node - no human figures in this thread ;)

For some examples I have used models from the Stanford scan repository (the Dragon has been cleaned up in Lightwave and Zbrush to fix a few topology errors). The Stanford scans are available from this link - http://graphics.stanford.edu/data/3Dscanrep/ - but please note their terms of use.

The first thing I'd like to point out is that as the Principled BSDF is an individual node it is easy to blend between multiple materials using a mask. The setup below is very simple but the concept is the same no matter how many materials and masks (procedural or image-based) are used.

Two complete materials are defined; a mask is defined using a Poser Tile node; a Poser Blender node is used to tell the render engine which material to render according to the values taken from the mask (a Cycles Mix node with the mask plugged in to the Fac chip could also be used).

(This scene uses a black material on the Background material zone of the Poser Ground, and a mid-grey on the Ground zone as I want to keep bounced light way down. There are two area lights, one in front and to the side, and one behind the prop. The prop itself is a simple rounded cylinder I made with a couple of levels of render subD applied.)

Next I want to talk about Specular as it was key for me when I was trying to understand the difference between Superfly and Firefly.

Specular in Firefly is a hack - it is used because raytraced reflections in FF, especially blurred reflections, are extremely slow to render, so specular is a means of faking them. Superfly however does raytraced reflections on everything all the time, which is why when compared like for like it is much faster than FF. Specular in SF is base reflectance (this can also be called direct reflectance or F0).

Base reflectance is the amount of light that bounces back to you from a material if you shine a light (imagine holding a torch) straight at it. With metals, this is high, with values around 60-100%. With non-metals the range is around 2-8%, with a few gemstones going as high as 16%, so the average for the vast majority of materials is 4%.

The Specular chip on the Principled BSDF appears to map 0-1 as 0-8% base reflectance, so at 0.5 it should be set to 4% for non-metals which will be good enough for a wide range of materials. This reflected light will be white.

When the Metallic is set to 1 it will override this Specular setting. The reflectance will be set to 100% and the reflections will be coloured by the Diffuse chip.

What all this means in practice is that most of the time Specular on the Principled BSDF can be left at the default 0.5 - and if the material is a metal, set that to 1 and forget about Specular. Simple!

So here’s a simple metal -

And a simple non-metallic material -

Base reflectance is not the same as fresnel reflections. These are reflections that occur when the light hits the material at grazing angles, and the beauty of this node is that it handles these automatically. No need to even think about them. In this scene setup the fresnel effect can be seen on the side of the cylinder as the light here is coming from behind the prop and hitting it at a sharp angle. The smaller highlight at the top centre of the cylinder is caused by the second area light in front of the prop, and therefore shows base reflectance.

This brings up another important property - Roughness. The physics are clear that as the angle of light hitting a surface approaches 90 degrees the reflectivity of that surface will approach 100%. This means that all surfaces behave like mirrors when the light hits them at grazing angles. But while the science might state this, it’s not what I see in the real world - a dead leaf never appears mirror-like no matter what angle I turn it to the light. Why not?

The answer is that the surface of the leaf is rough at a microscopic level. If you could see it in enough detail it would look like a mountain range, and the light gets caught, trapped and bounced around deep in the valleys. It cannot escape easily, or by the same route it arrived. Mirrors are smoother, and the smoother the surface the lower the chances of the light being trapped, and the easier it becomes for it to escape and bounce back in a straight line.

Therefore roughness is extremely important when defining a material. If the geometry defines the primary shape of an object, and the visible surface relief is defined by bump/normal/displacement, then the roughness defines the invisible surface relief, which has a huge effect on how the light is treated when it hits it.

The amount of light that falls on a surface does not change, so the amount of light reflected back from it does not change, but the greater the roughness, the more diffused and dull the appearance of that selected light.

Here the setup is the same but Roughness has been changed from 0.5 to 0.05 -

Now the Roughness has been set to 1, and the highlights are far more diffused. The amount of reflection is still the same though.

The Specular Tint setting is not physically correct, but is included for artistic control if needed. All it does is to colour the base reflectance by the Base Colour setting, but the fresnel reflections remain white.

The Clearcoat setting provides another specular layer on top of the material, as if it were wrapped in clear plastic. This material blends two Principled BSDF nodes using Clearcoat and Tinted Specular using a Cycles Layer Weight node set to Facing as a mask.

Now for a change of scene to look at SSS using this node. I've switched to the Stanford Dragon model, and this scene has a single area light placed behind and to one side of the mesh (as you can see from the shadow). The Ground material settings have stayed the same to keep bounced light contributions down.

First I've set up a basic non-metal material and rendered it -

Now I've set the Subsurface Colour to red which will contrast with the base colour, and set Subsurface to 1. I've ignored the other settings for now. The SSS has swamped the base colour, so 1 may be a little high ...

Before adjusting anything else though I decided to switch the method used from Burley to Random Walk. This is a new method which calculates SSS using the volume of the mesh, so should be more accurate. It does require that the mesh item be watertight i.e. does not have holes in it. The Dragon topology was checked and cleaned up before testing. The difference is subtle.

Now I have changed the Subsurface Radius from 0.1,0.1,0.1 to 1,1,1. This setting controls the depth to which the light will penetrate inside the mesh. Higher values mean the light rays will penetrate deeper, and this means that the light will scatter and bounce around inside the mesh further and be more diffuse when it exits, which has the effect of making shadowed areas appear brighter and softer.

The Subsurface setting is a multiplier for the Radius setting, so I turned it down by half. The result confused me for a while.

The Radius setting has 3 values - x, x, x - which are for separating Red, Green, and Blue. Changing the values so that red light scattered deeper than green or blue changed the result.

The effect was too strong so I toned it down by altering the Radius.

Changing the Radius to scatter blue light deeper gave this result.

It looked like the red Subsurface Colour was counteracting the Radius, so I changed it to white and got the result I had expected.

Switching the Radius setting back to scatter red deeper but leaving the Subsurface colour at white gave this result. It appears that the Subsurface colour intensifies the result of the Subsurface Radius settings, and the whole effect is then multiplied by the Subsurface value. As SSS is a volumetric effect, I figure the settings will need to be varied according to the scale of the mesh item.

I like this result.

Now here is an attempt to wrap it up into a more caucasian skin. I've added a bit of bump via the 3D texture node Turbulence. This is run through a Cycles - Vector - Bump node. Any grayscale procedural or image based texture can be plugged into the Height chip of the Bump node, and the amount of surface relief controlled by both the Strength and Distance values.

So the material -

These renders are not denoised and use higher samples; SSS like any volumetric effects I have found to be inherently very noisy but denoise can wipe out fine detail. The lighting has been changed as well - this is with a single area light in front of the Dragon.

Now with a single point light set to Inverse Square behind the Dragon.

Finally with both lights. I'll try to post some more examples of other uses for the Principled BSDF soon.

Thanks for sharing all of that. Even though it's not a "do these things" tutorial, it was very helpful for getting my head around the principles. And I learned some tricks too.

Thank you. The admins should pin this post. Very useful.

I agree, this should definitely be pinned, or all this useful information will get lost eventually.

Thank you for sharing !

SSS won't work with single-sided geometry as it needs a volume, but single-sided meshes are useful for foliage, feathers and dynamic cloth among others. Here are a couple of ways to add more options to those kind of meshes using the Principled BSDF with other Cycles nodes.

First, the Geometry node can be used as a mask to put a different material on the back-facing geometry. I made a simple ring, had the same setup as above on the Ground, used a single area light in front of the mesh, and set up this -

A Blender node could be used instead of the MixClosure - there is a lot of mix'n'match possible between Poser and Cycles nodes. An invalid connection will be indicated with a dotted line.

Now to add translucency to the same mesh. I've switched to an infinite light now. The translucency will only show up when the light is passing through the geometry so the direction of the light matters - to show this I've made the translucent colour red and the base colour blue.

Lit from the front.

Lit from behind.

Now combining back-face masking with translucency added to the back-facing material only.

Again, lit from the front.

And lit from behind.

Caisson, this has been most informative and reinforces much of what I have learned about PrincipleBDSF from Youtube. I'm looking forward to seeing more of your examples.

Thanks Caisson. I hope this info sinks in with folks.

excellent explanation! Working with PBR makes transitions between render engines a lot easier as well.

Here’s a practical example of the Principled BSDF plus translucency on an older mesh of mine. First I’ll post the renders - the only difference between them is the position of the light. Scene details - single infinite light with 0.5 shadow blur radius, white, 100% intensity, default Ground with a grass texture tiled on the Ground zone and a panoramic sky in jpg format on the Background zone. Renders are jpg’s from Poser, no post processing.

First the shader for the flowers. Pretty simple - one texture map for colour, one for roughness, both plugged into the node and the Specular set to 0.5 (which is the 4% average for base reflectance). The colour map is run through a Cycles BrightContrast node and that is used as the translucent colour, which is added to the output of the Principled node with an AddClosure node. (The only time I’ve ever used the AddClosure so far is when building translucent materials).

The shader for the leaves is a bit more complicated. I always try to break stuff down into pieces. The first bit is the maps - colour and roughness are simple. The height map is plugged into the height chip of a Cycles - Vector - Bump node, and I generally leave the strength at 1 and adjust the distance value. This node outputs a normal, and I plug this into any other Cycles node that has a normal chip unless I can see any reason not too ;)

I knew that I wanted translucency, but I also wanted to try to distinguish between the upper (very green, shinier, not translucent) and lower (rougher, more yellow, translucent) leaf surface. Now the geometry here is from Zbrush Fibremesh, which is a bit scrappy and all the leaf UV’s are stacked in 0-1, so I was trying to maximise variety in the render. After importing the maps I added the first Principled node and tweaked and test rendered til I was happy with that material; then disconnected that, added the second Principled node and made the second material; and finally added the Backfacing mask to mix the two. Lot of test renders - the rule, as bagginsbill pointed out years ago, is to change 1 variable then render.

Thank you

Quick example of setting up a texture set exported from Substance Painter. When the maps are plugged in they override the settings on the chips, which disappear. Make sure normal maps are in 8 bit not 16 bit format. These should be run through a Cycles - Vector - NormalMap node, and the Space set to tangent in order to work correctly.

This is the first HDR render I’ve done in years, so I won’t go into details as my understanding is woeful. The map is one that ships with SP, and I used transparent background in the render settings, then composited the grey background in Photoshop - and as I was there, ran a Curves adjustment and unsharp mask too.

Great examples. It will probably be my next endeavor to embrace Cycles. The sad thing, from what I know, is cycles won't render correctly or at all in Firefly, correct?

One of the biggest turn off's for me with DS is that many if not most published artists abandoned 3Delight and only create surfaces for iRAY now. I like the idea of having something for Firefly users going forward rather than abandoning that part of the user base!

Bumping this up since it looks like the site hides old threads, even if stickied.

Thanks ChromeStar - I'll try and remember to add examples from time to time!

So here's a load of balls. Plugging a Blackbody node into the emission chip on the PBSDF allows the colour temperature to be set in kelvin (K) - the render goes from 1800K (candlelight); to 3000K (lightbulb); to 4000K (moonlight); to 5500K (midday); and finally to 10,000K (blue skies).

That's pretty cool. Is there any possibility of controlling light falloff through the PrincipledBSDF node or does that become a separate process? I know how to do it entirely with cycles but I see no other alternative with your posted setup.

I think that would either be separate or involve plugging more nodes in, which then kind of defeats the point of the PBSDF. I'm using it as a higher-quality-more-versatile alternative to the Physical Root, so am trying to avoid complicated setups.

It looks like Blender 2.92 and higher has an Emission Strength input on PrincipledBSDF where you could plug in that LightFalloff node pretty easily. Not sure how Cycles upgrades are going to work in Poser. But see https://blender.stackexchange.com/questions/164075/how-do-i-change-strength-of-emission-at-principled-bsdf

That page also suggests that for us the solution would be Cycles --> AddClosure --> PrincipledBSDF with the other AddClosure --> an Emission node, so you can plug the LightFalloff node into the Emission Strength input on the Emission node.

It's not as clean as Cycles --> PrincipledBSDF but it's really not that bad.

caisson, I love you.

You have no idea how much this has helped me learn the new nodes.

There are no glass PBR shaders, or am I mistaken ?

There's a GlassBSDF: https://docs.blender.org/manual/en/latest/render/shader_nodes/shader/glass.html

You can also use it for other transparent shiny materials like water.