[Sidefx-houdini-list] Curves normals

Pablo Giménez pablogipi at gmail.com
Thu Aug 26 11:05:59 EDT 2010

I am rendering some poly lines as curves, using the 'width' attribute
to control every filament width.
That's all right.
Problem is that this geometry is created at render time and the
normals and texture coordinates are a little bit odd.
My main problem is that Mantra creates the needed geometry using the
width attribute but seems that is only shading the original curve
I mean the hair geometry is created extendin the shaded point,
perpendicular to the point of view, and the new geo seems to use the
same shading as the original point.
Is similar to what happens with points rendering, where the point is
shaded once, and then all the geometry created at render time around
the origian lpoint use the same shading from the original one.
So you don't have proper normals to make for instance a diffuse
lighting that gives you some "rounded" look.
I have tried the hairNormalVOP, creating my own tangents, created
texture coordinates with s going along the hair line from 0 to 1, but
the normals I got are just pointin towards camera, they are not doing
the "Rounding2 effect that is suppose to do this operator.
So is there any way to go away from the planar look of curves shading,
any way to have sense whre you shading point is in the new created
gemetry so you can for instance fake normals o apply any othe rtrick.
Un saludo
Best Regards
Pablo Giménez

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