Rendering Maya Hair properly....

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  01 January 2013
Rendering Maya Hair properly....

I'm trying to render maya hair with mental ray and linear worklflow but htere is no way I can shade the hair properly, no matter how dark I make the colors....I'm using gammanodes for the hair it still is extremely light. The scene is lit properly.
The possibilities to change the shading attribute of hair extrmely limited, is there a way to attach another shader or even paint FX to the hair. Tries those p_shaders (puppet) but they only work with fur and not hair....any ideas to get a decent look using hair ?!?

thanks a million
  01 January 2013
Hi. I read your shave thread and don't know what's going on there. I imagine you've given up on the shade route instead goin' with maya hair.

Maya hair, own it's own, never looks good. At least not by today's standards.... or ever standards set 5 years ago.

Yeah, I read you tried the puppet shaders, but instead do a search in this Maya forum (and sub-forums) for "puppet" not "hair". You'll find a wealth of info there such as Render settings.
Puppet being good for only fur and not hair is a huge load of crap. Forget Paint FX.

And you'll find some of my posts in those threads too.

The above links and threads were all well and good for learning but there was heaps of problems I had to work out on my own.

I've learnt a lot about maya hair (maya fur, actually) recently and finally found a good shading setup and character/hair relationship setup and lighting/render settings setup. And, of course, the affects of the shader's value tweaks etc. that makes something close to feature film quality.
My goal was a particularly hard one. Create something that looked good without using a compositor to blend everything together later.

So I was doing a rig with short fur like a mouse. I've heard people claim that long hair is harder than fur. Not true. There both come with there own problems that the other doesn't have, or not as much. (Of course, when it come to simulating hair, of course long hair is harder.)


My initial struggles in the beginning were:

PROBLEM: the blown out hairs particularly on the tips. Even with lights only in the front and no lighting aiming toward the camera... there were still blow-outs.

SOLUTION: Add a mia_photographic lens shader. Since I was using a linear workflow, I changed the gamma from 2.2 to 1.0 and increased the cm2 factor to areas between 20,000-45,000.


PROBLEM: The shading/colour attributes of the furDescription were crappy. Not enough control.

SOLUTION: Downloaded the puppet shaders and did it's wacky setup. It's like riding a bike once you get the proceedure down. These shaders are, indeed, as claimed by djx in his blog, much faster.


The bigger problems:

PROBLEM: For short fur, you could see the gaps of skin between the hair roots especially when the hairs aim straight at the camera. For longer hair, this isn't as much of a problem as the long strands sweep over a larger portion of the head with greater probability of covering those gaps.

SOLUTION PART 1: Increase hair count? Yeah, but then as you add hairs, of course it goes slower, but when you look at the silhouette of the character you loose that nice furriness because the hairs are more tightly compact.

SOLUTION PART 2: Design the fur to lean over and increase the tip curve value so it bends more inwards.

PROBLEM: (Also related to the above problem) : The skin shader's and fur shader's lighting never really look in sync. The hair doing self-shadowing (hair casting shadows on other neighbouring hairs) looked great. Turning the fur off, the self-shadows the skin made on itself looked fine. Hairs look great. The skin's self-shadowing looked great. Combine the two and perhaps where you'll find dark shadows of skin... you'll see a bright hair. Or the other way around. Bright skin with dark hair.

SOLUTION: So if the hairs are casting shadow on other hairs is good, then try to eliminate the visibility of the underlaying skin shader all together. How? Half the number of hairs of the furDesciption and create a 2nd one. So,for example, if the original furDescription is 1,000,000 hairs, reduce it down to 400,000 - 500,000.
With the newly created one, set it's hair count to 500,000 to 600,000 shorten it a little and lean the root and tip over so it's almost laying down on the skin's surface. Also add scraggle and have it a great crazy shape, but the goal is to have it lean over as much as it can. Almost completely laying down! Not fully. Since I was animating the character, you have to allow for
deformation. If the hairs are perfectly laying flat, when an elbow bends, for example, the hairs will infact be inside the geometry in parts. So in other words, the goal of *that* fur description is to fully cover the skin. The furry longer hair and short "leaning over" hair will play nice with each other and ther result is perfect lighting/shadows/self-shadows.

Another advantage of this is: 1. You have more control of styling. 2. You don't need to go down to the Details section and increase the noise value on the length making it greater than 0. Changing it's value here adds a tonne of render time. Even just a tiny value increase.

Also note: The root and tip bend, scraggle, inclination, length, baldness are all fast, however watch out for increasing the clumping value. It, too, when increased above 0, increases the render time calculation heaps. But remember, that by adding a second description, you don't really need to play with clumping and noise in the details dropdowns. It looks natural as it is.

All the lighting info you'll find in those links and when you do a search for "puppet". By the way, in the blogs etc., you may come across some info about adding a spotTK shader to a spot light. Don't have to, I found it useless.

I hope that helps you and others. I don't want others to suffer the pain i did.

P.S. Also:
Make sure your renderview window is set to 32bit. Right click anywhere on the render view window and you'll find it in there. Restart Maya.

Gamma nodes? What for? A procedural like a ramp perhaps, but not if you're using colour management and a Jpeg file (or any sRGB image).

What's your colour management settings? Give us a picture of the crappy renders, render settings windows etc.

Last edited by egglybagelface : 01 January 2013 at 08:19 AM.
  01 January 2013
I think he's using gamma nodes because Maya's color picker represents and also renders chosen colors in sRGB and never linear.
My opinions are always my own...and maybe a friend's, but never my employer's.
  01 January 2013
I should clarify.... paintfx is cool for designing and control but I meant the default shaders.... forget that....
  01 January 2013
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