First let me say I’m fairly new to blender and I’ve only done some minor projects other than the tutorials just to get a bit of variety in my practice.
I’m doing a jewelry and gemstone project. While looking for source material I came across a “Mystic” topaz. For those that don’t know Topaz can come in pretty much any colour. What intrigued me about the mystic variety is it goes through the entire rainbow of colours depending on how the light hits it.
I was wondering if this is even possible to reproduce in Blender and if so how would I do it. At first I wanted to do some simple gems as practice but after seeing this I’m feeling a little inspired so it will be dissapointing if it cant be done.
If you have never seen mystic topaz check out the link and image below.
That blendswap has gems showing dispersion. The gems are a single colour with dispersion simulated by splitting the RGB components of the gems and passing them through different IOR values. Thats not what the OP is asking for.
Some gems like mystic topaz exhibit a colour change effect which depends on the viewing angle (almost like iridescence). To simulate that you have to pass a different colours through a Fresnel or Layer Weight node.
OP - try downloading that blendswap file for your gem model/mesh - but apply the following node setup to it instead of the one supplied - it should get you pretty close (this is what I used in post #7)
Mystic Topaz is produced by coating the gem with an iridescent coat. Part of the colour you see will be from the surface of the gem (in much the same way as a soap bubble produces colour), part refraction/dispersion of the surface colours through the gem and part from reflection off the back faces.
It would be very difficult to reproduce a physically accurate representation of this effect, so you have to try and replicate the effect using techniques that are available.
The example I gave above is only a rough starting point. Perhaps look up materials that simulate the iridescent effect of soap bubbles (there are a couple around on these boards) and combine these with dispersive glass/gem materials (also available on these boards). You’ll learn a great deal about cycles by studying and tweaking these materials.