Rune Skovbo JohansenOct 16

I had an impulse to see if I could make a basic hair shader that doesn't require any specially made meshes or textures.

The shapes below are just standard Unity spheres and capsules and only a simple normal map is used; no other textures. Left is Unity's Standard shader; right is the same, but with brute force anisotropic shading, running the BRDF function up to 50 times and taking a weighted average.

Of course, non-brute force approaches are possible too, but way harder to make look good.

Show threadRune Skovbo JohansenOct 16
Ok, I think this hair shader experiment is done for now.
Show threadRune Skovbo JohansenOct 16

My partner saw the previous video and commented it looked like hair dye commercials. I had her help me tweak the parameters to look more natural. Increased normal map strength and slightly decreased smoothness did the trick. Parameters I did nothing to implement; they come from Unity's shading model.

I'm also messing with the parameters a bit in this video.

Don WilliamsonOct 16
Show threadRune Skovbo Johansen
I found some characters on the Asset Store and tried changing the hair material to use my shader. Luckily they all already had hair aligned vertically in the UV map, although not 100% for wavy/curly hair, which compromises my shader slightly.
(This asset: https://assetstore.unity.com/packages/3d/characters/humanoids/humans/npc-casual-set-00-326131)
Oct 16 at 9:59pmWeb
Show threadRune Skovbo JohansenOct 17

I intentionally turned the normal strength down since I thought that looked more natural. My interpretation is that the original materials used exaggerated normals to compensate for lack of anisotropic lighting, but a few people thought it looked too flat.

So in this video, in addition to the original materials (left), and my hair shader with decreased strength normal maps (middle), there's also my hair shader with full strength normal maps (right).

Show threadtoerrorOct 17
@runevision The guys with gel in do benefit from the enhanced coherency IMO.. The long / natural ones maybe don't want the exaggerated specular reflections ( again, opinions my own, I'm the last person to have an opinion on hair IRL ;) ) - for me, I'd consider using the base normal map to reduce the level of the specular reflections, but not add in extra gloss; This is because where you have a clump of hair, I'd expect it to self shade the hairs occluded from the light.
Show thread🌈 Andrew ☄️Oct 18

@runevision it seems the flatness comes from the normals of the geometry? A normal map may give smoother base normals?

It’d be interesting to see this with no colour texture and no hair shader. I’d want a baseline to have the specular highlight moving smoothly as it rotates, not jumping across planar surfaces

Show threadRune Skovbo JohansenOct 18

@bnut The people mentioning a flat look that I referred to meant that the hair shader looked flatter than the standard shader (left).

I'm not going to change the models or make custom made normal maps for them. The exercise here was seeing how far just a shader can get me without having to do anything bespoke.

Show thread🌈 Andrew ☄️Oct 18
@runevision that’s fair, although a model with a normal map isn’t bespoke imo - I was just concerned if that was it then it was throwing off the evaluation :)
Show threadtoerrorOct 16
@runevision Looks better, but it does lose some of the depth on more textured hair; Maybe just incorporating some lighting from the original normals would restore some of that lower frequency detail? ( or possibly just the shadows )
Show threadRune Skovbo JohansenOct 17
@toerror Ah, well I intentionally turned the normal strength down since I thought that looked more natural. My interpretation is that the original materials used exaggerated normals to compensate for lack of anisotropic lighting, since very strong directional normals can produce a crude version of it.
Show threadtoerrorOct 17
@runevision Hmm.. I'm really imagining a half lambert term pushed through AO, but maybe it would make it start looking like plastic again..