PBR Textures questions

General TouchDesigner Discussion
#1

3 PBR questions. My understanding is that there are 2 types of PBR material workflows. Those using SpecGloss and those using MetallicRoughness.

However in the PBR MAT there are slots for both Specular and Metallic and Roughness.

Is there a reason or scenario when you might want to have all slots defined? Or if you are defining a Specular Level Map should you leave Metallic and Roughness undefined?

If you have both albedo AND diffuse maps should you use albedo with PBR materials?

If you have a gloss map where would that be slotted, Roughness or?

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#2

Great questions! Would love to hear some official feedback on these as well. + 1

I personally leave specular out, and just use metallic / rough, but I do notice a slight change when I do stuff with specular, in addition to metal/rough. Not sure what the meaning of that is though.

I think albedo is another term for diffuse if Iā€™m not mistaken? I believe the mapā€™s purpose regardless of itā€™s name is to provide surface color info with as little lighting and shadowing information mixed in as possible. Like how stuff looks on a cloudy day etc.

Not 100% sure about gloss, would love to hear other thoughts there, but my understanding is that does not play a part in the pbr model touch has. I think some shader authors may include the maps necessary for the older shading model that works with gloss, so their sbar is more ā€œbackwards compatibleā€, but could totally be wrong about that.

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#3

Started studying PBR topic and ran into the same questions.

Maybe I found the answer to that one here. In Substance MetalRough workflow it is normally assumed that all dielectrics 4% reflective and this value for them is usually not defined separately. However, it can be overridden with Specular Level map: ā€œSome metal/roughness implementations, such as those found in the Substance toolset and Unreal Engine 4, have a specular control, which allows the artist to change the constant F0 value for dielectrics. In Substance, this output is labeled as ā€˜ā€˜specularLevelā€™ā€™ā€. So I guess you would normally want to leave Specular Level map empty, unless you have weird dielectrics that have weird reflectance values.

Glossiness I figure shouldnā€™t go to Roughness because in theory those maps are opposite of each other. So I got the same feeling as Lucas - probably PBR implementation of TD does not support SpecGloss workflow.

But definitely it would be nice to have more on these questions in the Wiki :slight_smile:

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