How to use the Reflection Map for Principled Shader?

(bentraje) #1

Hi,

I’m trying to use an old asset made with Vray.
It contains

  1. Diffuse
  2. Gloss
  3. Normal
  4. Reflection

1 to 3 are straightfoward with Gloss to be inverted for Roughness slot.
My concern is the Reflection Map. It is is a colored map and I guess it is use to tint a highlight but I’m not sure how to use it. I tried it with the “Sheen Tint” and the “Specular Tint” but there is no noticeable result.

You can see the maps here:

I also tried searching over the forum but nothing definitive like this one:


where the reference link is dead.

Is there a way around this?

Thank you for looking at my problem?

(Andrea) #2

I think this is useful!

1 Like
(Rob) #3

For PBR shading, there’s two ways of texturing. One is the ‘metal/rough’ workflow, and the other is the ‘specular/gloss’ workflow.
Both are different in the way they use textures for defining the characteristics of a material.

Allegorithmic has some really nice and free PDF’s on the subject. And due to the way both wokflows work, it’s not always possible to use the existing textures with conversion nodes to get the same results. Both workflows work with B/W textures to define gloss an metal, but the diffuse texture is defined different.
The old way of shading is not really useful to replicate in PBR with existing textures.

But in your case, you could make the material this faded brownish color, and stick with the first three textures to see what happens.

rob

edit:
Guides can be found here: https://www.substance3d.com/pbr-guide

1 Like
(John Malcolm) #4

You can completely ignore it when using the metal/rough workflow in the Principled shader. If it’s a metal object, which I’m guessing it is, then you should set metallic to 1.0 unless there are rust spots or whatever in places in which case you’ll need a map for that. The proper colour of reflections in metallic materials will be handled by the shader. You might need to look up suitable colours for the Base Colour though. This will vary depending on what type of metal it is and it’s from this value (or map) that the reflection colouring comes from (in metals)

I had a quick check on Poliigon which has some metal texture maps in both metal/roughness and spec/gloss. Try using the reflection map as the base colour in Principled.

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(CarlG) #5

Open up the original asset in VRay, check how everything is connected. Observe what effect each map has on the object and try to recreate those responses. That’s probably the only way you can obtain (close to) original intent. Some intents may not even be possible, I don’t know VRay. Even if it looks good, it’s not guaranteed that the asset is setup with PBR in mind or even physically plausible. Personally I don’t mind “cheating”, but I prefer knowing when I do.

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(Emir Sinan Gürlek) #6

Hi @bentraje ,
In addition to good responses above, as far as I know you must setup for ‘Specular Workflow’ as seen below:


The reason for that is because your textures originally exported in this manner; metal colors come from the specular (reflection) map and metal parts in albedo is -probably- just black.


If you try to setup for ‘Metalness Workflow’, you’ll be missing metalness map (You can’t use reflection map for this, because metalness map must be black and white). Also metal parts in albedo map must have color information (which probably you don’t have). It’s true that Inverted Gloss map = Roughness map.


Also check this link:
https://help.poliigon.com/general-information/the-differences-between-metalness-and-specular-workflows

1 Like
(pixelgrip) #7

sometimes it is usefull to take a look at the documents from the product it self (in this case vray)

here you can see the settings for the given reflection map explained.to me the most important setting is the filter color,that acts as RGB reflection multiplier.

this could be rebuild with a custom node build.

https://docs.chaosgroup.com/display/VRAY3MAX/Reflect+or+Refract+Map+|+VRayMap
https://docs.chaosgroup.com/display/VRAY3MAX/V-Ray+Material+|+VRayMtl#V-RayMaterial|VRayMtl-reflectionReflection

in this thread i tryed to rebuild the vray reflection material behave.now i would build it a bit different but have a look.

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(bentraje) #8

Thank you all for your response. It has given me enough information.

In summary, based on the posts above, here’s what I can conclude:

  1. The reflection map is not needed in the PBR Metalness workflow
  2. Both the diffuse, reflection and specular map was used to determine the “metalness” of an object.
  3. For the sake of argument, if one wants to really use the reflection map, it is to create a base color map (i.e. some vooddo conversion from (Diffuse Map + Reflection Map) = Base Color)
  4. It is undesirable to plug the reflection map directly to the base color. The reflection map was meant to determine the color of the reflection/highlights and not the color of the whole object itself.

Thanks again. Have a great day ahead!