[Sidefx-houdini-list] Anisotropic work around?

Peter Riel peter at basecampvfx.com
Sat Feb 18 09:46:21 EST 2006


Hi,

   I was hoping a kind soul could explain to me in somewhat plain English how 
I can render anisotropic highlights when using polygonal surfaces containing 
faces with less or more than 4 verts. I have tried to get my head around the 
recent topic on sidefx.com, "creating a brushed metal shader". A few 
technical explanations were given in vex code, which I'm embarrassed to say 
is completely out of my league... I don't even know how to approach it... 
most of the time I'm able to hack something together... but with vex surface 
shaders I'm quite lost. While I would love to take the time to learn how to 
program shaders in mantra, it's unfortunately an undertaking that requires a 
great amount of time and playing around. 

To me personally this is one of the areas in houdini which frustrated me the 
most. Take the example of a default anisotropic highlight shader, it should 
be able to render out a polygonal surface correctly, without the user having 
to dig so deep as into vex code. It baffles me why there is no more detailed 
explanation of this in the documentation. The line- "Avoid using the 
Anisotropic Specular model on non-subdivided polygonal geometry because it 
will look flat shaded." This is only partly correct as poly geometry built 
with faces NOT quads, are rendered wrongly by the specular lighting model 
anyway, even with the subd turned on. 

Another issue for me is also why the rendered output from a subdivide sop, and 
a polygonal model with 'Polygons as Subdivision Surfaces' turned on in the 
render tab has different output. But that's another story...

Anyway.... back to banging my head against the wall... wohoo ;)


Peter.






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