Hello, sorry if my English is bad.
Personal work that ends with a diamond .
The basic idea is simple: is it possible to realize a Fresnel function supporting the imaginary part with the nodes?
Assuming that ND and K are = or greater than 0, the function can then be recalculated, giving a node like this:
I use this scene for the following examples
Basically, it produces the same result as the internal blender node.
The difference appears with the use of the imaginary part, I use the wavelengths 650,525,480 nm
The data used is taken from https://refractiveindex.info/ and .ior file
Metals:
Aluminium
Chromium
Copper
Gold
Gold White
Gold Rose
Gold Purple
Iron
Silver
Zirconium
The imaginary part can be converted into an absorption coefficient, and used directly in cycle
In addition, the function supports total reflectance: simply invert the ND/K value pairs into, a shortcut is made using backfacing
Diamond whith and without total relfectance
We get this
Gemstone
Amethyst
Aquamarine
Beryl Yellow
Diamond
Emerald Ural
Garnet Orange
Sapphire (medium blue)
Tourmaline Yellow
Liquid
Biodisel
Water
For the rest, I wanted to reproduce the blue diamond of France, the French blue
https://museumdiamonds.com/french-blue/
https://www.researchgate.net/figure/The-original-laser-scan-data-from-the-lead-cast-of-the-French-Blue-top-when-cleaned-of_fig3_274674367
The modelling was simple, I use the ND of the diamond and the K of the sapphire, I did not find the data of the Hope diamond.
HDRI textures come from https://polyhaven.com/hdris
the rendering is rather heavy, and the denoiser does not like it.
I hope I didn’t do anything wrong with the forum and my first post.