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

Mark Elendt mark at sidefx.com
Thu Oct 26 13:29:38 EDT 2006


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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