Matte Translucent Material Node

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Taka
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Matte Translucent Material Node

Post by Taka » Wed Apr 17, 2019 10:28 pm

Hi,

Just a quick question. Isn't it supposed be a "Diffuse Color" instead of a "Reflection Color" in the node?
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FarbigeWelt
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Re: Matte Translucent Material Node

Post by FarbigeWelt » Thu Apr 18, 2019 6:18 am

According to my knowledge diffuse and reflection colors are not the same. Diffuse is for matte objects like paper and reflection for specular objects like glass or mirrors.
This might be a bit of question for starting users.
But there is actually a big difference if you think about it.

Well, the final question is, what kind of material is matte transluscent.

If its surface reflects light in any direction like matte does and the material does not have any Bragg angle of total reflection, you were right and the more appropriate terminus here was diffuse rather than reflection color.
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B.Y.O.B.
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Re: Matte Translucent Material Node

Post by B.Y.O.B. » Thu Apr 18, 2019 8:09 am

I have wondered about this as well. Dade, can you tell us more?
But I guess it's a thing from the distant past, from LuxRender times, so the developer who originally chose this name is probably not around anymore.
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Dade
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Re: Matte Translucent Material Node

Post by Dade » Thu Apr 18, 2019 9:38 am

The logic is (or was, like B.Y.O.B. wrote, this stuff has its root in code written 10 years ago): one is a scale factor used when light is transmitted and the other when it is reflected. "diffuse" would be a bit generic/confusing because light is always "diffuse", both when is transmitted and when it is reflected in mattetranslucent material.
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Re: Matte Translucent Material Node

Post by B.Y.O.B. » Thu Apr 18, 2019 10:05 am

Maybe it should be renamed to "Diffuse reflection color"?

I think fixing terminology like this could be a part of v2.3.
There are some more cases like this one:
- "Matte" is not really the right term - usually "matte" means something related to alpha/compositing/masks. We should replace it with "diffuse", which from what I know is the standard name for hemispheric scattering on a surface
- The roughness input of most materials has a range of 0 to 1, however the "roughmatte" material has the "Sigma" input with range 0 to 45. This is needlessly complicated/different from a user point of view and roughness maps don't work out of the box. I think the "roughmatte" material should expose a 0-1 roughness like every other material and do the conversion to 0-45 internally.
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Re: Matte Translucent Material Node

Post by FarbigeWelt » Thu Apr 18, 2019 10:06 am

Matte transluscent is like its sibling glossy transluscent still somerhing miraculous, at list for me.

If matte transluscent delivers always diffuse light, reflected or transmitted then if reflection and transmission colors are both 1,1,1 light gets dispersively rayed on both sides of an any thick object whereas both sides ray 50% of received light in any direction.

Glossy transluscent is not that easy because here some part of the received light should bounce in specific directions like a mirror would reflect them.

This means there is for transluscent material
Reflection, diffuse
Reflection, specular
Transmission, diffuse independent on thickness

and if there were absorption
Transmission, clear dependent on thickness

Did I overlooked something?
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Re: Matte Translucent Material Node

Post by Dade » Thu Apr 18, 2019 10:10 am

B.Y.O.B. wrote:
Thu Apr 18, 2019 10:05 am
Maybe it should be renamed to "Diffuse reflection color"?
Yes but use "Diffuse transmission color" label too, I mean, they are symmetrical.
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