Spherical Rainbow Glitter material in Cycles?

Question

Does anyone know how to replicate this pattern in cycles?

I've been keeping it simple by just saying that every one of these flakes is a perfect circle (though they clearly aren't) and generating these circles with a voronoi texture. I was generating a wave texture with a color ramp to use for the rainbow effect, but I have very little control over which flakes are emissive/highly reflective, and which are not. I've played with plugging the circles into a normal map, but I'm still not getting the contrast in reflectivity.

Answer 1

I had an idea that was bugging me, and it took three tries. Here is the final version. It's still not a perfect match because unlike the reference the dots are not monochrome but multicolored if you look closely. But I think it's very close to the reference.

^{Example render (Cycles)}

I used your idea to create the dots/flakes through a Voronoi texture. Then they are stacked in 5 layers where each background layer is a bit darker to simulate 3D depth.

The dots can be created using Voronoi > Distance output and the help of a Color Ramp or Map Range node. This is also a mask for the Mix node. The Voronoi > Color output gives each dot its own color. The problem with this is that I want the individual dots to be solid colors, but in the overall image I want them to match the background texture (the "rainbow"). I have no idea how to realize this, so I leave them multicolored, that is, I just mix them with the background.

^{Glittering dots shader}

So mix the background with the created dots and the result is again used as background for the next layer. Darkening is done with the help of a Hue/Saturation/Value node. The dots of the last layer are lightened and slightly desaturated to make them shine more.

To organize the nodes, group the nodes that will be used to create a single dot layer. Now it is better to use a Map Range node instead of a Color Ramp because you want to control the values from outside the group.

^{Glitter Dots shader group}

The "artistic" normal map is generated by separating the color channels, keeping blue at 1 and randomizing the red and green channels. Here is a similar question for even more glittering: Orange peel effect does not work

The color of the default "flat" normal map is HEX 8080FF.

^{Glare nodes for the compositor}

Last but not least, use a HDRI as world background, and activate the Bloom effect for Eevee. For Cycles, it's better to use one or two glare nodes in the compositor.