fluffy rambles: VRChat avatar, referred colormaps edition

VRChat avatar, referred colormaps edition

September 23, 2022 12:37 AM (9 months ago)

Today I put my literal shower thought into action, and redid the pigment mapping stuff to use a color lookup table instead. And hoo boy, were there a lot of pitfalls; namely:

Unity defaults to loading color textures as sRGB, and does so by linearizing the color space
The default wrapped texture lookup causes all sorts of fun boundary conditions to happen
Default texture compression completely hecks up texture values which rely on precise lookups
Oh right, interpolation can’t solve precision issues

But hey, now I have a working colormap that more or less replicates what I had last night, and then some:

This version of the shader lets me do a lot more stuff, for example giving the different eyes different colors (and different colors for the upper and lower eyelids, even), and also adding textures to the irises. I can also make the front, sides, and back of the necklace tag different colors.

Here’s the pigment map and color map for that setup:

I also wrote a dumb C++ program to bake a pigment map and color map into a fallback texture:

Also, authoring these color schemes is WAY more difficult than just moving sliders around in the Unity editor. I have to be very fussy with a bunch of gradients, especially for the eyes, but the advantages are worthwhile, I think. Just being able to define more color swatches and have more control within them is a huge advantage.

Of course, there’s a pretty big disadvantage in that I wouldn’t be able to use this to author color themes on-the-fly in-game (at least, not without using a multipass shader that renders out the colormap texture on-the-fly), but I’ve kept my previous swatch-mapping shader around and the pigment modulation channel is at least compatible between both shaders, so nothing prevents me from having both shaders be available in-game to switch between.

Oh, anyway, some of the things to keep in mind:

Pigment maps need to have their color mode set to linear (i.e. disable sRGB) and their format set to RGBA 32 Bit and/or set their compression to “none”
This approach is very sensitive to color bleed, so there need to be decent gaps between the UV islands and also a lot of bleed from the respective pigment map regions
Color maps need to have their wrap mode set to “clamp” and should probably have mipmaps disabled

Anyway, yeah, this is working pretty okay! Even if I don’t ever get the critter fully set-up the way I want, I’m really happy with where it is right now.

It’d sure be nice if I could figure out a better workflow for previewing the pigment map on the critter’s actual surface though. Photoshop at least had a way to map a layer to a texture on a 3D object at one time, but heck if I can figure out how to actually do it.