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

nicholas pliatsikas nicholas.pliatsikas at gmail.com
Tue Jan 10 18:42:43 EST 2012


Thats not a bad idea either :) a different technique of course I will need
to try that out. One other method would be to use material ifds and
instance delayed loads then use the instancepoint expression to switch the
matifd to what ever is needed, this would require i a bunch of preset
matifds.
But it would represent the fastest method of instancing especially if your
shaders are heavy production level ubershaders like the one we use at axis.

Easiest setup will be the method i described, if your up for the tech stuff
then theres plenty of choices that are way more optimal :¬)

On Tue, Jan 10, 2012 at 11:31 PM, Dan Wills <gdanzo at gmail.com> wrote:

> 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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