Author Topic: PBR Guide Vol 2 Figure 48 sRGB values for metals  (Read 6103 times)

hi there,

when looking at the chart Fig. 48, there are some metals, where sRGB values are listed.

Can somebody tell the right value for pewter and or tin, please?
(It is more of an alloy, and not a pure metal, I know)

Or are you guys just "eyeball" it via the roughness and take base color from image reference or so?!
I´d like to have a link to a comprehensive chart for all know materials, real world measured, hehehehe



cheers
Last Edit: January 22, 2016, 02:14:52 pm

Hey elowan,

maybe this helps you: http://www.nicoptere.net/dump/materials.html

I'm not even sure if those values are correct, just try it out ;)
For some metals I'm not even searching for correct values. I often choose something between two I know the values of.


Best Regards
Environment Artist - Twitter

Great, thanks a lot!

now... can you tell, how this:

Pewter   
ambient     0.105882 0.058824 0.113725 1
diffuse    0.427451 0.470588 0.541176 1
specular   0.333333 0.333333 0.521569 1
shininess   9.84615

 translates into Substance /Painter/Designer)?

best regards

Great, thanks a lot!

now... can you tell, how this:

Pewter   
ambient     0.105882 0.058824 0.113725 1
diffuse    0.427451 0.470588 0.541176 1
specular   0.333333 0.333333 0.521569 1
shininess   9.84615

 translates into Substance /Painter/Designer)?

best regards

Hi Elowan,

It is difficult to tell as the values could be in linear or sRGB. Also, the values are not designed for PBR data. I don't think that site will provide the info you need in this case.

Pewter is tricky. Its a metal alloy (mix of several metals). It is 85–90% tin with the remainder commonly consisting of copper, antimony and lead. It can also oxidize very readily so it would have a different appearance if its polished or not. Its one of the few metals that will be both rougher and significantly darker when oxidized. It will be tough to find the exact values. In cases like this, its best to research the material and see if you can derive some clues at to the values you should pick. I would look at reference and then try to extrapolate values based on what you know about the material.

I'm sorry I don't have an easy answer on this one : )

I use this list to get the IOR of various materials. The IOR for lead and copper is on the list. You can use the IOR node in Designer to enter the IOR to get a value in sRGB. Its going to come down to some educated guessing : )

http://forums.cgsociety.org/archive/index.php?t-513458.html

Cheers,
Wes

Wes



Cheers,
Integrations Product Manager / Training
wes.mcdermott@allegorithmic.com
Twitter: The3DNinja

Hey Wes,

thanks for that in depth answer and link!
I think, I get what you mean ;)


Cheers!

Sorry Wes, I am just confused by now ;)

How comes IOR into play? Ok, there is the node that can set a custom IOR value and output some color - now - where goes that color output? Is this only working with alloy specularity and spec/gloss workflow?

It is nor suited for PBR metal/rough, I believe?!


Cheers

Really not that easy to setup a material, like pewter... I want to do a pewter material for unity/alloy shader.

In SD, there is the node for setting a custom IOR value.
The right value can be obtained from the list, you linked.
I supect the output value (a RGB color) of this node to be plugged into the "specularity" channel of alloy shader.

But the thing is, alloy only takes that speculartiy into account (use it) for non-metals.
Like when alloy shader registers a metallic input (white) in the other packed channel, specularity value is ignored for
that areas.

In case of a nearly full metal material, setting a specularity/IOR value would make no sense at all, because it will
be ignored...

So I am at the same point, as I started on how to create a pewter material - maybe I just should not care about what is "correct"
and just take some aluminum material and tint it a bit and so on...

edit: I´ve found, that Titanium is close to Lead, regarding IOR
Last Edit: January 28, 2016, 04:10:50 pm

Really not that easy to setup a material, like pewter... I want to do a pewter material for unity/alloy shader.

In SD, there is the node for setting a custom IOR value.
The right value can be obtained from the list, you linked.
I supect the output value (a RGB color) of this node to be plugged into the "specularity" channel of alloy shader.

But the thing is, alloy only takes that speculartiy into account (use it) for non-metals.
Like when alloy shader registers a metallic input (white) in the other packed channel, specularity value is ignored for
that areas.

In case of a nearly full metal material, setting a specularity/IOR value would make no sense at all, because it will
be ignored...

So I am at the same point, as I started on how to create a pewter material - maybe I just should not care about what is "correct"
and just take some aluminum material and tint it a bit and so on...

edit: I´ve found, that Titanium is close to Lead, regarding IOR


HI Elowan,

Yes, sometimes you need to go a bit more visual in terms of what is right. Peweter is a tough example. You are right that you will not be using the specular channel. This is for non-metals. I would say for the reflectance value, you will want to use the reflectance value for lead and not worry about the exact IOR. The IOR is what is going to give you the reflectance value. You could use our titanium and lower the value as well.

Cheers,
Wes


Integrations Product Manager / Training
wes.mcdermott@allegorithmic.com
Twitter: The3DNinja

Thanks Wes!

I not manage to find out, where I could actually change the IOR of the standard titanium or how to put together a new material in SD, (PBR metal rough workflow!) from scratch with a custom 1. color reflectance, 2. IOR and 3. metall and 4. maybe a normal map/grunge. The PBR-Material nodes I´ve found, are kind of static in IOR manipulation (if you choose a metal material)

After getting a bit frustrated, I blended some Aluminum and blueish steel together, to get a lead/prewter like material in Substance Painter.

https://forum.allegorithmic.com/index.php?topic=8557.msg41553#msg41553

Cheers!
Last Edit: February 02, 2016, 08:35:19 am