Free Comprehensive PBR Guide

[elchicoconinsomnio]

Ok, understood. Thank you very much for your explanation

[Wes McDermott]

First of all, thank you a lot for this guide, it is concise and has very good explanations and image examples.

However, I've got some doubts regarding the differences between the spec/gloss and the roughness/metal approaches when mapping reflectance.

As far as I understood, in the spec/gloss workflow, for a metal material you will paint it black on the base color map, and the corresponding F0 color value for that metal on the specular map. But, in a roughness/metal workflow, how should it be done? I guess you'll just apply white on the metal map (because it's metal), and paint the corresponding F0 color on the base color map, right?

Now, when dealing with non-metals, in spec/gloss you'll paint the diffuse color on the base color map, and the F0 value on the specular map. But in roughness/metal workflow? I thought you were supposed to just apply a base color and set the metal map to black... but then where is the F0 value applied? Can you apply it to the metal map instead of setting it to full black? apply an additional specular map with the F0 value (I think UE4 lets you do this)?

Sorry if next volume is planned to clarify this with more examples.

Hi,

Good questions : ) Cyrille has posted the information.

via @Cyrille Damez
With non-metals the F0 value is very small and does not vary a lot between materials (except maybe for gems). The intensity of the specular reflection for non-metals is usually better changed by setting the roughness accordingly. As a consequence, in earlier implementations of the metal/roughness workflow, there was no way to change the F0 value for non metals and it was set to a constant (usually 0.04). Now some implementation also use a grayscale "specular" map to specify the F0 value for dielectrics. In Designer it corresponds to the usage "SpecularLevel". It maps linearly F0 values from 0 (black) to 0.08 (white), the default value being 0.04 (mid-grey).
Again, in practice the roughness map will make much more visual difference, and most existing non-metallic materials have an F0 value very close to the default.


In Vol. 2, this will be covered in-depth as well. There is a specific section on F0 dielectrics for metal/rough and spec/gloss. In the metal/rough sections, it is discussed as specularLevel channel input.

Cheers,

Wes

[elchicoconinsomnio]

Thanks! looking forward to read that vol.2!

[jehuty]

Download the Free guide
http://www.allegorithmic.com/pbr-guide

Thank you very mutch for sharing, i learned a lot of the guide.

[Fabian F.]

The best thing about this Thread: I have an answer of what I have to use in Substance Designer to get a F0 Value.
My Question is now: Is there a place where I can look up what output in Substance refers to what kind of desired map?
What I mean is that I really have bo idea what the differences are between the specular, the specularLevel and the specularColor outputs. There also is a reflective output and it confuses me a little

[Wes McDermott]

The best thing about this Thread: I have an answer of what I have to use in Substance Designer to get a F0 Value.
My Question is now: Is there a place where I can look up what output in Substance refers to what kind of desired map?
What I mean is that I really have bo idea what the differences are between the specular, the specularLevel and the specularColor outputs. There also is a reflective output and it confuses me a little

Hi Fabian,

The good news is that volume 2 will fully explain all of the maps and processes. It should be available next week : )

Specular has a different meaning for metal/rough or specular/gloss workflows. In metal/rough, the specular for dielectrics is hard-coded to be 0.04 (linear value) or 4% specular. They shader handles this. For metals, you then place the metal reflectance value in the base color map and the metal map indicates to the shader which areas are metal and which are not.

With metal/rough, you can override the hardcoded value by the shader using the specularLevel output. This is just a output that tells the shader to use a different value for dielectric F0.

In PBR, you don't use the reflectivity output. For specular/gloss workflow, both the dielectric F0 and metal reflectance values are placed in the specular map.

So with PBR you have either metal reflectance in the base color indicated by a metal map for metal/rough workflow or a specular map for dielectric F0 and metal reflectance values for the specular/gloss workflow. The specularLevel is an extra level on control for dielectric F0 for metal/rough workflow. With specular/gloss, you already have full control over dielectric F0 in the specular map.

Cheers,

wes

[Fabian F.]

Then I'm looking forward to the second vol.

As far as I understood is when I use a specularLevel in Metal/Rough I get a "combination" between Metal/rough and Spec/gloss?
And what I don't really understand is how I replicate the metal-map in spec/gloss. Because a pure spec map has not the same reflections as a metal-map, right?

I really want to check out the pros and cons about both workflows and how I can narrow the gap between both. When do I use spec/gloss and when metal/rough? Is it just preference? Most of the time I use metal/rough. Just because I like it and in UE4 it fits really good.

[Wes McDermott]

Then I'm looking forward to the second vol.

As far as I understood is when I use a specularLevel in Metal/Rough I get a "combination" between Metal/rough and Spec/gloss?
And what I don't really understand is how I replicate the metal-map in spec/gloss. Because a pure spec map has not the same reflections as a metal-map, right?

I really want to check out the pros and cons about both workflows and how I can narrow the gap between both. When do I use spec/gloss and when metal/rough? Is it just preference? Most of the time I use metal/rough. Just because I like it and in UE4 it fits really good.

Hi Fabian,

Vol. 2 will explain both workflows and their guidelines. You can use either workflow. There isn't a time to use one over the other. The implement the same guidelines and data. The difference is that you author the maps differently. Its just a personal preference on how you want to work. I use metal/rough as I like the workflow better.

Cheers,

Wes

[artzfx]

Volume 2 is out, but page down http://www.allegorithmic.com/pbr-guide#Download_guide

[elchicoconinsomnio]

Downloaded! Took a quick look and it looks VERY useful.
Thanks!

[artzfx]

Woohoo got it .  Thanks Wes. 

[ronmayland]

Nice job wes. Super documented and explained, thank you

[artzfx]

Is the PBR Metal/Roughness Validate node mentioned on page 24 coming in 4.6.2?  looks like a great tool for SD

[Fabian F.]

Is the PBR Metal/Roughness Validate node mentioned on page 24 coming in 4.6.2?  looks like a great tool for SD

Yes, as it is also mentioned in the Article.

[elowan]

Great material, thanks a lot!