Cornell University Cracks The "glow" of Blond Hair

Blender's renderer and external renderer export

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bmud
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Cornell University Cracks The "glow" of Blond Hair

Post by bmud » Mon Jul 24, 2006 10:10 pm

Here's the article I found on BoingBoing.net:
http://www.boingboing.net/2006/07/24/be ... _hair.html

Image
To quote a little bit from the article:
The problem is that light traveling through a mass of blond hair is not only reflected off the surfaces of the hairs, but passes through the hairs and emerges in a diffused form, from there to be reflected and transmitted some more.
con't:
Marschner and (grad student Jonathan) Moon's algorithm begins by tracing rays from the light source into the hair, using some approximations of the scattering and producing a map of where photons of light can be found throughout the volume of hair. Then it traces a ray from each pixel of the image to a point in the hair and looks at the map to decide how much light should be available there.
Here's a link to the white paper.
http://www.news.cornell.edu/stories/Jul ... ir.ws.html

I am curious if we can model some similar behaviour with nodes that fakes it just enough.

cessen
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Joined: Tue Oct 15, 2002 11:43 pm

Post by cessen » Tue Jul 25, 2006 1:54 am

As I said on Elysiun, it sounds like they're just applying photon mapping to hair, so it's nothing groundbreaking. The only thing that might be original in it is whatever algorithm they use to approximate how the photons should scatter in the hair--but I'm guessing that won't be too groundbreaking either. I'll have to read the paper to be sure, though.

Mind you, I'm not trying to belittle your post or anything. Just pointing something out.

Anyway, I do suspect that it could be faked fairly effectively in Blender once the node system for materials becomes more robust. At the moment I don't think there are enough nodes to do what would be needed (you'd need to be able to plug in information about the light sources, the camera, etc.). And it very well may involve some compositing tricks as well (especially for back lighting).

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