Anisotropy for horse hide?

Eric Chadwick

Looking for examples of anisotropy maps for complex surfaces, like the kind of shine across a black horse in the sun, how the specular bends across its back.

I suspect a flow map would work fine for this, depending on the renderer.

I've done a bunch of searches, can't seem to find any examples though.

Noors

The Order:1886

At 3:58

Yep flow/direction map painted in 3d and an anisotropic shader.

Basically what they were doing there
https://polycount.com/discussion/98983/how-to-paint-flow-anisotropic-comb-maps-in-photoshop
But with better tools.

Some hair/fur grooming plugins can also generate the data to bake a direction map. But that means grooming real geometry.

poopipe

Hair cards usually infer direction from UVs so you can get away with just flow but for something like this you need a third component for it

We used a custom tool that averaged a bunch of painted direction vectors in a texture last time we had to generate a load of furry animals - if I were starting from scratch I'd probably just bake off a groom (dpdu/dpdv in Arnold) as it'll give better artist feedback

Eric Chadwick

That's a neat example, thanks Noors.



It looks like they're painting in object space, but I would think they'd want to convert to tangent space for better compression, and probably also strip the blue channel. Perhaps Mari is in object space and HDR color just to keep it lossless and performant while in the tool, but then they postprocess it? Would you want OS for the final game asset for some reason?

Noors

I dont think OS maps can work with deforming meshes. Didnt mess with aniso for a while but i think in Unity, the channel uses tangent space. Looks like their tool is also using a voxelized version of the mesh. So maybe mari tool is in OS for voxel version then converted in TS with the mesh. My 2 cents.

Looking again, i don't think it's an OS map. Colors would be more consistent with the axis and there would be no texture seams. Object space is independent of uvs orientation.

Eric Chadwick

A neat online tool for painting flowmaps. Not nearly as nice as Mari, but it's still pretty neat.

https://cables.gl/p/ntZfmv

thomasp

Painting flowmaps is a thing in Substance Painter as well btw. https://substance3d.adobe.com/documentation/spdoc/flow-map-painting-143327274.html

I'd try with a groom first and see if that's practical to bake. This painting stuff .... it usually looks like something but you'll see the light once you get to compare.

poopipe

What you don't get with flow maps is progression along the hair strands  and that's pretty vital for UV independent anisotropy. 

This thread inspired me to try and write a direction map painting tool - I won't say I failed but it's really slow so I've got a load of work to do..