my favorite that i made out of the rock set i made back in june:
first step was making the model - i did this in nomad sculpt for iPad (which is also releasing a desktop version soon!?) essentially just made the base shape, and then boolean'd a bunch of spheres out of it before sculpting it to make it more rocklike.
if I was making this for an actual videogame i would then have sent it to blender to retopo. but i am not making this for a videogame i am making it for a sparkly gif so i do not need to retopo it. you do not want to see the blender view. but i will show you anyways.
next up was the texture - i knew i wanted to have streaks across the rock as a sort of roughness map, so i opened it up in procreate and made a few different maps in red, green, and blue, drawing strokes along the contours of the rock with different rake brushes. i then just plugged this into a to-normal-map converter after making it varying levels of greyscale.
and here's what the rock looks like with just the color texture on it!
i have each color affect the material in a different way. as a base, i'm using a mix of diffraction grating iridescence for the rainbow effect (with the grating distance turned low enough so the effect is just subtle enough to change gradually while the object spins), sparkles (classic), rim lighting, and environment reflections.
for the red channel - this was essentially just the reflection and iridescence - no sparkles and no rim lighting. this was the sort of "base". since there was less reflection on the green and blue channels, they served as a bit of a roughness map.
the green channel was no reflection, yes everything else (sparkles, rim, iridescence). and the blue channel was essentially just the green channel but times 4, with the extra addition of a higher grating distance in the iridescence, making it way less subtle. the green was layered on top of the red base, and then there were only a few bits of blue scattered around as accents. here's the rock again with just that map texture.
and here's what it looks like (from left to right, top to bottom) with just the red channel, just the green channel, just the blue channel, and also all channels but no normal map:
(lastly if there was no red, black, or green, it was just everything added together like normal)
the normal map did end up pulling a lot of weight, since as you can tell in the top left one, even without a roughness map there are parts that are "shiny" and parts that aren't just due to how condensed and noisy the normal map gets at the non-shiny parts.
anyways, all that together and you got the end result! thanks so much for reading!!