[Sidefx-houdini-list] HDK : Pos using UV Attribute

Andrew D Lyons tstexture at gmail.com
Tue Mar 18 11:57:03 EDT 2008


Try this:

vertex split sop - use promote attribute (vertex uv to point)
attrib create sop - store P ($TX, $TY, $TZ) in some temp var (Porig).
point sop - put this in P field ($MAPU, $MAPV, $MAPW)

These should put your model in uv space. Once there you should be able to
spatially subdivide in even uv segments. To get it back to cartesian 3D
space:

Put Porig back into P. (Hopefully you've used one of the subdivides that
interpolates point attrs for new subdivs.)
If the new points are out in one axis, you may want to dubdivde in both
spaces, and just pull a relatiive position vector from uv space to displace
the point in cartesian 3D space.

Hope that helps....

Cheers




On 18/03/2008, Jaideep Khadilkar <iamjaideep80 at yahoo.com> wrote:
>
> Hi Brian...
>
> I already tried using Primitive attribute. But it does the same thing as
> primuv expression. It uses prim_attribute function of Vex and the help of
> this function says,
>
> Evaluates the attribute string att for primitive pn at the parametric
> location u, v.
>
> And I don't want to find the Position on Parametric u and v, but texture u
> and v.
>
> I hope u can help me.
>
> ----iamjaideep80
> (Jaideep Khadilkar)
>
> brian goodwin <brian.r.goodwin at gmail.com> wrote: I think by using the
> primitive attribute in VOP's, it should give u the
>
> solution.
>
> let me know if u need some help setting it up.
>
>
> On Tue, Mar 18, 2008 at 2:59 PM, Jaideep Khadilkar
>
> wrote:
>
> >  Hi All...
> >
> >  I want to find position of a point on a surface using its uv
> attributes.
> > "primuv" expression gives me the position, if the surface is NURBS, but
> it
> > uses orignal NURB uv to calculate position and doesn't use texture uv
> > atrribute that we modify.
> > I have a polygon model with UV texture attribute from 0 to 1. Using the
> uv
> > texture attribute, I want to add some points evenly spaced in the uv
> texture
> > space(like a grid) and on the corresponding positions on the model.
> >
> > How to do that???
> >
> >
> > ----iamjaideep80
> > (Jaideep Khadilkar)
> >
> >
> > ---------------------------------
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>
>
>
> --
> brian
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Andrew D Lyons | Digital Artist | http://www.tstex.com
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