[Sidefx-houdini-list] Anisotropic work around?

Peter Riel peter at basecampvfx.com
Sun Feb 19 12:18:43 EST 2006

Hey Jim,

  Yes, it's surprising there is no updated anisotropic shader that works on 
polys. Especially since polys are pretty much all conquering these days.
 I use anisotropic highlights often, not just on metals... it gives you yet 
another way of hiding that awesome CG phong specular we get by default... ;)

As far as I can understand from the topic on the forum, there is a way to 
calculate smooth tangents for the highlight shader, but for a fool like me to 
implement it in a vop network is another story. 


måndag 20 februari 2006 01:17 skrev jrutherford at stclaircollege.ca:
> Hey Peter:
> I think that the default anisotropic lighting model is based on Greg
> Ward's lighting model which is .... ahhhhh...
> anyways for something like brushed metal, you are getting that long thin
> specular because the shader is finding the x direction and the y direction
> using something like
>  vector xdir = normalize (dPdu);
> Anyways that works great for a surface but with polygons, the houdini
> default gives you that kind of specular on every single polygon which
> looks like crap ....but is exactly what the shader is supposed to do...
> so what is the workaround and why doesn't Sesi have a default that works
> on polys like Maya...hmmm...probably some patent thing...
> I think Maya is using some sort of Photon Tracing to get it to work but
> I'm probably wrong...
> You'll have to talk to the overly caffeinated ex oboe player for that one
> which I think in my own humble way is what he has been sort of talking
> about in his other thread.
> Jim

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