[Sidefx-houdini-list] HOW: Random Point Color For instances

Dan Wills gdanzo at gmail.com
Tue Jan 10 18:31:11 EST 2012


If you're doing a large number of instances then the method Nicholas
describes works, but can be a bit slow to make ifds.

We experienced this on a recent project and found that a nice way to solve
it was to write out a bgeo containing the points that you're instancing
onto, with whatever attributes you need on them, id for example.

In the shader, we then used the "point cloud open" and "point cloud filter"
VOPs to filter attributes from one point at the constant position (0,0,0)
transformed from object into world (ie at the origin of the instance).
Unintuitively, the radius had to be increased a bit, probably because the
scene scale was quite large.

This scales pretty well when there are a lot of instances, and is also
great if you want to pass lots of data to them.
d

On Wed, Jan 11, 2012 at 7:31 AM, nicholas pliatsikas <
nicholas.pliatsikas at gmail.com> wrote:

> Look into using a material sop and assign your shader to the points on the
> material sop as an override on your shader parameter of choice using
> rand($PT). Or use the expression  rand(instancepoint()) directly on your
> shader that's assigned to your top level instance object. You Will need to
> add to the seed number in the random expression to insure the random value
> is different for red green and blue parm values etc
> On 10 Jan 2012 20:33, "Alvaro Castaneda" <varomix at gmail.com> wrote:
>
> > Hi
> >
> > I can't seem to find how to do this
> >
> > I just want to vary the CD attribute at each instance
> >
> > I'm just instancing geo into a bunch of point and want
> > them to be slightly different color.
> >
> >
> > Cheers!!
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