Specular highlights on hair with cycles

I am having trouble getting specular highlights on particle hair to work in cycles.
I got the hair particles themselves to render quite realistically in Blender internal, but the shadow buffer lighting required for that to work just didn’t match with the soft raytraced lighting for the rest of the scene, so I finally tried to do it in cycles. While everything else certainly looks better now, the hair just doesn’t really work with the glossy shaders.

After a lot of testing I finally managed to get an approximation of shiny hair but it’s still very noisy and doesn’t really look like glossy strands but more like bright paint sprayed onto the areas where the lights are reflected.

Sorry for the dark image. You’ll have to zoom in a little to see what I mean. I already tried to render it out with a lot more light, but that only seems to make things worse.

The image took about 1200 samples and about 2 hours on my machine, so I guess it’s not a problem of too few samples.

Any hints on how to improve cycles managment of glossy shaders would be much appreciated.

(And yeah… I know the eyes and teeth are much to bright and the hair is still not very realistic overall:))

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If you haven’t seen it, you might find this helpful: http://www.blenderguru.com/videos/how-to-render-hair-with-cycles/

Can you post a node setup for your hair material?

Thanks for the reply. I’ve watched Andrews tutorial, but - to be honest - I didn’t actually try it with the Sintel .blend.

Anyway, here’s the node-setup ( I assume the problem is in there):

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Problem solved. Kind of…

The mistake I made was using area lights in cycles. Since they can now have materisals with nodes and such, I assumed they were finally usable like with Blender Internal. (I’m using Blender 2.67b by the way)

It turns out they do not work too well with the glossy shaders. It seems as if you need to have a visible light - i.e. a mesh light - in order to have it reflected by the glossy shader. At least that seems to be the case for very low roughness values or single ray / mirror-like reflections.

After I changed all the lights to mesh lights, the reflections in the hair strands worked a lot better.

Of course now I need to find out how to tone down those bright reflections in the eyes…


Hmmm… I may have to correct myself here. After some more testing I’m not so sure if it’s really about wether you use mesh lights or not.

For the last image I also mixed the zero roughness glossy shader with another one at about 0.200 roughness which might have smoothed out the highlights in the hair strands.

So, while I somehow solved the problem, I still don’t have a clue how I did it exactly.

I wish there was a way to get some bullet-proof facts about these things. Anyone out there who can deliver those?