Creating "Comb" maps
polycounter lvl 19
I read this thread: http://www.polycount.com/forum/showthread.php?t=97215 and remembered I'd made something similar a while back.
I figured out how to make a vector based direction map using Paint shop Pro's picture tubes a few years ago and realized I needed to get around to sharing it. So here you go, free to use. *edit* now with example video thanks to Kurt Russel Fan Club making a modded Xoliul shader.
[ame=
http://www.youtube.com/watch?v=YBR--OTtBD4&hd=1]"anisotropic comb map example"[/ame]
http://www.poopinmymouth.com/process/hair_tutorial/ng_hair.html
[ame=
http://www.youtube.com/watch?v=P9KRnh3cROw&hd=1] "comb map creation"[/ame]
I figured out how to make a vector based direction map using Paint shop Pro's picture tubes a few years ago and realized I needed to get around to sharing it. So here you go, free to use. *edit* now with example video thanks to Kurt Russel Fan Club making a modded Xoliul shader.
[ame=
http://www.youtube.com/watch?v=YBR--OTtBD4&hd=1]"anisotropic comb map example"[/ame]http://www.poopinmymouth.com/process/hair_tutorial/ng_hair.html
[ame=
http://www.youtube.com/watch?v=P9KRnh3cROw&hd=1] "comb map creation"[/ame]
Replies
Well, when I put this together 4 years ago, Photoshop had no equivalent of picture tubes, I'm pretty sure it still doesn't, but would love to be surprised. PsP is cheap enough that if a studio were to take up this technique you'd just get one license, and it takes maybe 10 minutes to make a comb map, so someone could just bang them all out really quickly.
http://www.unifycommunity.com/wiki/index.php?title=Anisotropic_Highlight_Shader
hmm, i am wondering if you can modulate color based on stroke direction? doesn't seem like too hard of thing to accomplish. i know psp is cheap i just like streamlining my workflow between as few programs as possible. i do most of my texture work now in mudbox, i will dig into the brush settings today and see what i can do. thanks for this tip tho, i wanted to blow my brains out with a character recently whose entire hair style was braided braids, tied together with braids.
I do have unity, but not pro. Any chance this can be ported to max?
But yeah, awesome tutorial, and no, the shader wouldn't be too difficult to translate at all, although it would take some time.
Here's a shader mod for Xoliul that lets you use anisotropic specular. Under spec, select "Anisotropic" and then beneath the Normal Map area there's some new values to enter your Tangent map (the flow map). Here's how it looks with your flow map and a simple desat for the spec map:
Edit: It almost certainly won't work with the new shader interface so I'd keep it separate from your default shader and just use it manually when you need to.
Edit 2: Updated shader so it's much better
I'll answer this later today with an illustration as several people have been confused on this.
That's awesome, but I can't seem to get it to work. Check this screenshot. With anisotropic unchecked, specular is in the right position for a blinn/phong type. When I tick anisotropic (with the comb map in the tangent slot) it turns into a fresnel type look. What am I doing wrong? I tried all combinations of flip green/red under tangent as well. Even before entering any maps, if I toggle "anisotropic" it will flip from a phong type correct specular hotspot to this fresnel ish specular.
Here's an updated version. Just make sure that also once you assign your tangent map you click that "tangent map" checkbox. All other settings should be okay this time.
Updated the original tutorial to explain better: http://www.poopinmymouth.com/process/hair_tutorial/ng_hair.html
To simply further, let's look at a braid. This is a photograph, a braid texture would never have such strong highlights painted in, but it shows clearly how the anisotropy flows in different directions based on the hair orientation. Imagine this is your diffuse texture.
Now let's pretent this photo is a texture, and we have assigned the 3d model an anistropic shader with only a single global value. The green arrow represents the angle I chose. The highlights look great on the hair chunks going from upper left to lower right, but are completely wrong on the chunks going from upper right to lower left. If we rotated the direction to make it fit for them, the first chunks would break. In this example we have no comb map, simply a normal anisotropic shader with a global numerical input value in the form of an angle (0-360).
But with a comb map, we can use a different orientation value per-pixel! This will allow for the anisotropy to correctly follow the diffuse and normal map directions. In the same way a shader reads the value of a normal map pixel to determine what angle it should light the object, a shader that uses a comb map to control anisotropy will read the angle from the pixel in the comb map to determine anisotropy angle. This would be what your comb map would look like, the values correspond to the "direction" the hair is flowing. The shader can read this and correctly orient the anisotropic highlight.
Awesome, got it to work. Just made a quick video showing with and without on the actual Delilah model. Uploading now. This is great, exactly what I was looking for! Thanks so much dude. Do you mind if I host this shader file and link to it within the tutorial page?
No problem - I don't mind if you host it at all, but because it's basically the Xoliul shader I'd ask Laurens first.
[ame=
!
It contains angle information the same way a normal map does yes. The point is how to make it in a human way. There isn't a way to get a comb map from baking a tangent space normal map off a high poly, if that's what you were thinking.
I added a new wiki page with this and some more stuff.
http://wiki.polycount.com/FlowMap
here's a quick aniso shader with tangent map - thanks for the xoliul version - using the whole tangent map in the same way as TS normal map was simpler for me to get than the approach I had taken from "Scheuermann_HairRendering.pdf"
here's the link http://dl.dropbox.com/u/5440025/aniso.fx
I guess I was too late to really help much, but I will add the secondary specular highlight after Scheuermann and see how it looks in the next days. You can put a channel in the alpha of spec map which allows to shift the spec a bit up and down the surface. It might be hard to do this in the tangent map when authoring - again it is ust ripped from Scheuermann so I claim no credit, just exploring the area.
I've pondered this authoring quagmire a few times over the last 12 months at work, and my plan is thus:
1) create hair on a reference model based off asset but posibly higher poly count
2) comb, style, coiffure etc.
3) run script, (as yet not created) which could:
a) snapshot splines from hair
b) matchup spline knots and poly verts from styling cage
c) project spline onto tangent space of vert to get a relative direction of strand per vert
d) store this info somehow (texture, vertex colour, something)
e) post process into something usable.
It might just work? any other ideas I'm willing to have a pop!
http://www.polycount.com/forum/showthread.php?p=1582749#post1582749
Thanks for the inspiration, poop!
[ame="
You need to use it on your Hikune character, especially once Maph gets this shader working , as the double specular will really help sell her blue hair.
You guys should try loading these into toolbag, the content looks pretty similar to what our app spit out and I believe the anisotropic shader still supports these direction maps.
How would one go about loading this into toolbag?
The -only- problem I see with a 2d solution is seams, painting anything in tangent space gets hairy on seams.
Here try it out:
http://dl.dropbox.com/u/2336353/AnisoComp_Anim.mov
I guess one work around would be to plot seams along the natural hair grain, which most people probably already do? It wouldn't be as good as painting over seams on the model but it would help disguise the discrepancies.
Yep that was the one, funnily enough it was the only asset that was made with the tool and made it in game.
If you open toolbag, you can assign a anisotropic shader from the shader dropdown, which should give you the option to load a direction map, sorry don't have it installed here so I can't be more specific, you should figure it out though.
Yes, you'll notice in most photos of hair, the highlight also has a surrounding bit that is closer to the hair's actual color but a bit more saturated. Sells the "hair-ness" of it.
Coming up with the picture tube to create a comb map to control anisotropy direction was all me, but I was pretty sure someone, somewhere was also using a per pixel map, most likely generated with proprietary in house tools, and I wanted something off the shelf.
This looks great so far!