I think there is an ambiguity in CG jargon for material channels

#1

I was having a look in the specks of this product :

What is a flow map ?
What is a Deposition Map ?

And under which material channel should I put those ?

Also Texture Heaven has Roughness, AO, and Rough AO where do these go ?

And still don’t understand what the diffusion channel does and if the Diffuse map should go there instead of colour.

There should be a unification in the terminology of similar things like color, albedo and diffuse

I think that shiness, metallnes and specular maps are also the same thing.

Aren’t Bump and Displacement maps essentially the same thing ? The only difference is how they are interpreted by the renderer.

#2

The first two have nothing to do with material channels. Deposition is a map showing the deposit of silt, sand or earth on a terrain – like when a river leaves sediment in a tributary. A flow map shows the flow of a substance – presumably water in this case – and where the landscape has been eroded. You would most likely use these as different colour maps, but they can be used in various channesl, depending what effect you were trying to achieve,

For example, you could use the flow map to make the terrain shiny, as if there’s water on it, and the deposition map can be used to alter the colour of the landscape.

AO – or ambient occlusion – can go in the Diffusion channel. It will just make certain areas, which occlude light, slightly darker. Frankly I wouldn’t worry about Rough AO; I’ve never used it.

Yes, the Diffuse map is much the same as Colour or Albedo (though Albedo can be slightly different in some workflows). This goes in the Color Channel, unless you are using the PBR system when it goes as a Diffuse layer in the Reflectance Channel (which I admit is a bit confusing). Reflectance is another whole discussion.

If you have a Glossiness map, it’s simply a Roughness map inverted. You can use it in the Reflectance Roughness channel, but switch the black and white levels from 0 to 1 and vice versa, to invert it.

Bump is very different to Displacement: Bump is more of a CG optical illusion – it only looks bumpy, but the surface is flat, whereas Displacement actually generates geometry at render time.

#3

Yes, I know what the difference between bump and displacement is as a final result. But as an input texture these two have nothing different. They both use the same grayscale information to translate into height. Right ?

So Roughness is just an alpha map for the Blurriness of the reflections. Glossiness is the invert of the later and should go under the Reflection Strength or Specular Strength ?

Is the Bump under the Reflectance Channel the exact same as the Bump Channel or does it affect only the reflectance ? Honestly I’ve been ticking that Bump channel as I did ages ago in conjuction with the Reflectance… I didn’t know i was doing it wrong.

Bump and normal maps have the exact same effect but the information is encoded differently that’s why I did not try to compare them.

#4

Yes, bump and diaplacement are both greyscale bitmaps, but for displacement, you should use a 16-bit map for best results.

Roughness/Glossiness should really go in the Roughness channel in Reflectance, if you’re using a PBR workflow. I guess you can control Specularity with it, but the result will be different.

Yes, I think you can use the bump under Reflectance. I tend to just use the usual Normal channel. I do have my own way of using Reflectance – I tend to use it in Additive mode with the Color channel. I find using a Diffuse layer can be noisy when rendering. Frankly C4D’s PBR workflow could do with a bit of refining/simplifying. And don’t forget to add a Fresnel value!

#5

I will just add that Bump and Normal aren’t the same either. A good Normal map is far superior to a Bump map, as it mathematically alters the angle of the rendered pixel, so as optical illusions go, it’s much more effective.

#6

Also a note on Normal maps - it works with ambient lighting, so no matter what the environment your ‘bumps’ will appear.

Bump maps only have an effect in direct lighting - thus no direct light no bump.

I think fstorm is the only render engine I have seen that treats bump mapping similar to a normal map, which is quite cool tbh.

#7

I totally agree. This bump option in the reflectance channel is highly misleading. How different is it from the traditional bump channel?
Same for the diffuse layer in the reflectance channel, although I understand that a PBR workflow requires the use of a diffuse layer rather than the color channel.
We need a unification of the material system.

#8

Not sure that’s true, bump makes surface changes even with bounced light and hdri skies etc. Unless you’re referring to ambient light as something else?

#9

Its exactly the same. The difference is you can do bumps per layer. So a rough woodgrain diffuse layer with a smooth polished clear coat on top.

#10

Well yes you are correct, bounced light and hdri also produce light.

Sorry I should be more specific - ambient light as in a skylight without GI. (probably not very common workflow these days I suppose).