[Sidefx-houdini-list] Point Attributes to Instanced Geometry

Robert Persons robert at adtechinc.com
Thu Oct 26 16:36:08 EDT 2006


Thanks Mark,

Stamping of shaders is a rather creative solution!

This is what I suspected; that only shaders can be applied to instances.

Perhaps an RFE would be to have attributes on points override the same
attributes on instances ... it would make this a lot simpler. 

Thanks for your help!  Also thanks to Brian and Jean-Claude!

Robert Persons

-------------------------------------
Robert Persons
Adtech Communications Group
952-944-6347
-------------------------------------
mailto:robert at adtechinc.com


-----Original Message-----
From: sidefx-houdini-list-bounces at sidefx.com
[mailto:sidefx-houdini-list-bounces at sidefx.com] On Behalf Of Mark Elendt
Sent: Thursday, October 26, 2006 12:30 PM
To: sidefx-houdini-list at sidefx.com
Subject: Re: [Sidefx-houdini-list] Point Attributes to Instanced
Geometry

On Thursday Oct 26 at 12:08, Robert Persons wrote:
> I'm using point instancing and would like to transfer attributes to
the
> instances.  In this case I'm instancing a 3D house model to points on
a
> 2D poly.  Each house has several materials. I'd like to transfer the
> Alpha and Cd attributes from the points to all the points on the
> instanced model.  I could use the copy SOP but we're talking of
hundreds
> of instances so the geometry would get too dense . I really need to
use
> point instancing in some way.
> 
> Any Ideas?

The easiest idea would be to stamp a shader on each instance.
It's not possible to modify the geometry of the instance, but it is
possible to change the surface shader.

Here's a simple .hip file which shows what I mean.

The important things to look at are:
    - The expressions for the diffuse color in the plastic SHOP (in
      the points object)
    - The shader SOP is creating hard strings on each point rather
      than indirect references to the SHOP (so that stamping works)
    - The shader SOP creates point shaders (rather than binding to the
      primitives).

If your house model has multiple shaders, this gets a little trickier,
but it's do-able, just a little more work and clever thinking
required.





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