Author Topic: Anyway to customize Measured Metals to simulate real world jewelry alloys?  (Read 1533 times)

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Offline Dan75

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The measured materials in KS7 look great but pure gold, silver or platinum are not generally used to make real world jewellery.  Most jewelry is made from 9, 14, 18, or 22ct yellow, or rose (red) golds, or 9, 14 and 18ct white golds.  Platinum and palladium in jewellery is normally only 90-95% pure and in any case many white gold jewelry pieces will be rhodium plated.  Attached is a image illustrating some subtle but real world jewellery metal colors.

Keyshot might be much more convenient for jewelry renderers if it had both an easy way to custom tune the 'color' of the measured precious metal and/or easy to select pre-defined metals as follows - with the most important being those differentiating the shades of yellow and red/rose golds:

Yellow Golds - 9, 14, 18 and 22ct
Red/Rose Golds - 9, 14 and 18ct
Non-rhodium plated White golds - 9, 14 and 18ct
Rhodium
Sterling Silver 


Is the Keyshot team aware of the differences between carat gold alloy colors and is there any roadmaps to accurately reproduce them, or at least provide an easy way to consistently create them?

Offline jordantheperson

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This is exactly what I would like to know as well. Using a custom color for metal does not reflect light/color correctly. I work in the furniture industry and there are various metal shades in patinas and types of metal. I would like to use an image to define the color of metal but unless its "measured" it will not look right.

Offline DriesV

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The Measured Metal Presets in KeyShot 7 are characterized by so-called 'complex IOR data'.
You can find this data in the form of Sopra .ior files. Unfortunately, such data can be hard to come by freely on the internet, as they require careful and intricate reflectance measurements of physical sample materials.

A workaround (albeit less accurate) is to use a 'Color Gradient' texture with Gradient Type set to 'View Direction' for the metal Color (Metal Type Color).
This allows to control the view dependent colors with a gradient.
Also, using 'Metallic Paint' with a high 'Metal Coverage' can be a good option for metals. That will give you even more control over the reflection colors.
Attached is a simple example scene with a Multi-Material to switch between a Metal and Metallic Paint variation for a gold-like finish.

That being said, there are methods out there to derive the reflectance color based on the relative metallic composition of alloys. Would that be a useful way of defining metals in KeyShot?

I hope that helps.

Dries

Offline Dan75

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Dries,

Thank you for the in depth response and example scene - they are useful techniques.

Yes ! - from the point of view of jewellery - it would be great if we could keep the 'measured' metal material AND there was a relatively simple way to create an alloy eg. platinum 950 = 95% platinum plus 5% other metal e.g. Copper.  Or Sterling silver = 92.5% silver and 7.5% copper - then we could use a slider or similar to fine tune the color results without losing the 'measured' property.  This wikipedia post on colored gold alloys might be useful https://en.wikipedia.org/wiki/Colored_gold

Offline MWo

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Dries,

Thank you for the in depth response and example scene - they are useful techniques.

Yes ! - from the point of view of jewellery - it would be great if we could keep the 'measured' metal material AND there was a relatively simple way to create an alloy eg. platinum 950 = 95% platinum plus 5% other metal e.g. Copper.  Or Sterling silver = 92.5% silver and 7.5% copper - then we could use a slider or similar to fine tune the color results without losing the 'measured' property.  This wikipedia post on colored gold alloys might be useful https://en.wikipedia.org/wiki/Colored_gold

This could be achieved with labels. So you need a dummy material like diffuse. Then use the material graph (pro feature) and apply a silver and additional a copper (metal, anisotropic or measured) and combine them with the color composite node. Then add a color to number to drive the alpha of the overlaying metal. One of the output parameter should define the e.g. 7.5% value.

Without testing it - it should work. Maybe I found some time next week to give it a try. Or some user here upload an example?!

Hope that helps

Cheers
Marco PS: written on a mobile

Offline Søren

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Hi Marco,

No that will not work very accurately. What you are describing is a material composed of e.g. 7.5% area coverage of copper and 92.5% silver. To be precise, the material will appear as if the two metals have been sprayed onto the surface in different proportions- this will not give exactly the same appearance as an actual alloy of the two metals.

I would like to add though, that if you can get hold of measured values of the complex refractive index of the alloy you can load those data directly into KeyShot.

Søren
« Last Edit: July 02, 2018, 06:53:24 am by Søren »

Offline Dan75

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Hi Søren and Dries,

Perhaps Marco is on to something with his suggestion?

Maxwell discussion .ior files here: http://support.nextlimit.com/display/maxwelldocs/IOR+files

Maxwell freely provide all the different gold carat materials zip files which contain .mxm format on their website here:

http://www.maxwellrender.com/materials/ (search for gold)

Within the zip files they also make available .ior files for other gold alloy component metals such as palladium and rhodium (Bonus!)


Within Maxwell Studio if you open and apply to a model an .mxm file for example for 18ct yellow gold - you can see immediately that the resulting material is a Normal Blending of Layers of .ior files for gold, silver and copper weighed 75%, 19.2% and 8.75% respectively.

While this might not be as accurate as an actually measured ior for 18ct yellow gold the result is good enough for most jewellery modellers ;)

Is there a way to blend keyshot measured metals in this way?

Offline MWo

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Søren is right. Cause if I mix copper and zinc I will never get brass.


But thanks for the link!

Offline Dan75

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Thanks for the quick reply Marco.  Perhaps you can help me since I am new to Keyshot, but just to try the exercise myself I couldn't see how to use color composite in material graph to combine two 'materials'.  Should this be possible or can it only combine textures?  Did you try what you had suggested earlier in the thread and perhaps you could screenshot your material graph to show how you did it? 

I was able to get a blend effect by putting a color composite in front of each measured metal and then adding them as labels to the diffuse material you suggested  (screenshot attached) - then I just adjust the overall alpha in each composite node but is this a logical way to do it?


Offline MWo

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Here's my example of the first idea of a solution. But as Søren suggested, this is just a workaround and no guaranty of physical correct representation.
But you asked for using the color composite node.

Hope you / we find any way to solve this?!


Cheers
Marco

Offline MWo

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The Measured Metal Presets in KeyShot 7 are characterized by so-called 'complex IOR data'.
You can find this data in the form of Sopra .ior files. Unfortunately, such data can be hard to come by freely on the internet, as they require careful and intricate reflectance measurements of physical sample materials.

A workaround (albeit less accurate) is to use a 'Color Gradient' texture with Gradient Type set to 'View Direction' for the metal Color (Metal Type Color).
This allows to control the view dependent colors with a gradient.
Also, using 'Metallic Paint' with a high 'Metal Coverage' can be a good option for metals. That will give you even more control over the reflection colors.
Attached is a simple example scene with a Multi-Material to switch between a Metal and Metallic Paint variation for a gold-like finish.

That being said, there are methods out there to derive the reflectance color based on the relative metallic composition of alloys. Would that be a useful way of defining metals in KeyShot?

I hope that helps.

Dries

That is a very cool example. Thank you Dries!