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

Alvaro Castaneda varomix at gmail.com
Tue Jan 10 19:50:02 EST 2012


Thanks guys I'm not doing a super huge scene so the simple instancing
worked great will keep this as reference for the future on bigger stuff

Thanks again
On Jan 10, 2012 6:43 PM, "nicholas pliatsikas" <
nicholas.pliatsikas at gmail.com> wrote:

> 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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