Marschner hair model

[jinso001]

I am also starting the implementation of "Marschner hair model" using Renderman or houdini SHOP like you.

So I read the paper. But it's too difficult to implement the Marschner hair model, because there is no pseudo code.

I found the some information relate with "Marschner hair model" in GPU Gems 2.

Here is site for reference.

http://developer.nvidia.com/book/export/html/42

There is pseudocode summarizing the shader in GPU GEMS 2.

=========================================================================================

// In the Vertex Shader:

SinThetaI = dot(light, tangent)

SinThetaO = dot(eye, tangent)

LightPerp = light –– SinThetaI * tangent

eyePerp = eye – SinThetaO * tangent;

CosPhiD = dot(eyePerp, lightPerp) * (dot(eyePerp, eyePerp) *

dot(lightPerp, lightPerp))^-0.5

// In the Fragment Shader:

(MR, MTT, MTRT, cosThetaD) = lookup1(cosThetaI, cosThetaO)

(NTT, NR) = lookup2(CosPhiD, cosThetaD)

NTRT = lookup3(CosPhiD, cosThetaD)

S = MR * NR + MTT * NTT + MTRT * NTRT

=========================================================================================

Is it same to paper contents? I think not.

I think they use the lookup table and some information in paper is omitted for efficiency.

So could you tell me which pseudocode has to add and change for result like your works?

Thank you for reading.

[ssh]

Now shader supports texture maps and ramps!

You can texture diffuse or each specular component or all of them.

Ramps serves for remapping computed colors based on hair length.

Now it's much easier to make roots darker or tips brighter.

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This greatly saved me time.

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ssh_marschner_hair.otl

[Pazuzu]

Thank you!!!!

[abvfx]

owww yea

Thanks soo much Sergey

[abvfx]

Initial images were a bit large, used attachments in the next post.

Edited May 3, 2011 by phrenzy84

[abvfx]

Here are a few low sample tests ive done (with my regular Houdini guinea pig )

Stubble / 5 o' clock shadow version

Unshaven / Rough

George Clooney (Syriana)

[Netvudu]

hey, actually that´s very cool phrenzy.

So I understand that´s the Houdini stock hair tools coupled with Sergey´s shader?

[abvfx]

indeed

[ssh]

Nice images, phrenzy!

Will he talk?

[abvfx]

Dunno.

He is basically my Houdini character guinea pig, I test pretty much everything on him. But he needs more work. I'm gonna finish modelling him, and Then im gonna rig him.

I want him to be a pretty worthy production asset, Im gonna be playing more with UV range and thinking about splitting maps beyond the 0-1 range.

But I have quite a few more characters/creatures i wanna work with in Houdini, this guy is the test bed. Also im gonna try and see how i can use your shader for long hair.

Long hair is pretty tough in Houdini right now.

[ssh]

This hair model should work very well with long hairs.

If there will be any questions regarding shading setup feel free to ask here!

[abvfx]

This hair model should work very well with long hairs.

If there will be any questions regarding shading setup feel free to ask here!

Oh yea im sure, ive seen your tests on vimeo, i just meant in terms of grooming long hair. Its very hard to control using the fur system.

[Marc]

Long hair is pretty tough in Houdini right now.

I successfully used Blender to groom some long hair and use the exported curves as guides in Houdini fur tool. Blenders long hair grooming tools are fantastic, and you can't beat the price .

M

[ssh]

Blenders long hair grooming tools are fantastic, and you can't beat the price .

That's really interesting!

How easy is it to make a braid with such tools?

[abvfx]

I successfully used Blender to groom some long hair and use the exported curves as guides in Houdini fur tool. Blenders long hair grooming tools are fantastic, and you can't beat the price .

M

Really! Wow i thought it was only possible to do that in shave. I've envied Blender's grooming tools since Big Buck Bunny.

Cant wait to try it out.

Dunno about the price, seems like a scam

[ssh]

Update:

Added opacity ramp.

May be useful to fadeout hair tips, for one thing.

Edited May 24, 2011 by ssh

[ssh]

Sorry, double post.

Download the shader here.

ssh_marschner_hair.otl

Edited May 24, 2011 by ssh

[abvfx]

Ahhh i wondering if this was gonna get added. Even though you can adjust the thickness from root to tip it can still make hair look a "hard".

Once i get long hair grooming between blender and houdini working, finally i will be able to create a female with softer looking hair.

Thanks for all your hard work Sergey.

[abvfx]

Ive been messing around some and found it a little difficult to get light-haired results without cranking up the intensity of the lights (which would over expose the model). I can use the light linker to select all the brighter lights just for the hair but I think it might come down to the parameters.

Primary, Secondary, Overall spec all have bright colours, diffuse has a decent intensity which is a ramp from a very very light grey to almost pure white. What other parameters should i be messing with?

(btw ignore the bad hair grooming + render its all a work in progress )

[abvfx]

Apologies for the double post. Here is a clearer pic.