How to create a non-uniformly colored gem?

[quinyu]

I would like to render a gemstone which has a non-uniform color, but instead would use an image as a color map (alignment options are like the usual, but I need a volumetric effect, not a surface decal.) To get a more visual idea, think ametrine, watermelon tourmaline etc. See pictures attached.

Thank you for all suggestions in advance

[Ed]

quinyu -

This is an interesting challenge.

As a proof of concept (I'm not trying to duplicate a real stone here), I made a label, reduced the opacity to 50% in Photoshop, and saved as a png.

I applied this semi-transparent label to a gem material and adjusted many of the gem's material settings to get this result.

I think it will work better with a label of perhaps 25% opacity as the internal quality of the gem does not come through if the opacity of the label is too high.

Not a true volumetric effect, but due to the label transparency, it may be close enough.

I would experiment and please share your results.

Ed

[Dylan]

That's a very good workaround Ed. I didn't think opacity on labels would work for that, your workaround gives a new use for labels.

[starboy]

how beautiful