RE: shading geometry instanced to particles

["Halfdan Ingvarsson" <hingvars(at)Softimage.COM>]

Title: shading geometry instanced to particles

Currently it's not possible.

 

There's a missing feature in mental ray that would've made this easy to support, which would've involved attaching particle userdata on each instance. In current versions of mental ray, when attaching userdata to an instance, it modifies any existing userdata on the same instance which fails miserably when trying to apply that userdata on a instanced hierarchy (delete becomes extremely hairy). This is because userdata is defined as a linked list, where the tag id of the next userdata is stored in the userdata header itself, rather than a flat list with indirection (as is done for shader lists). We're working with mental images to address this.

 

 - ½

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From: owner-xsi(at)Softimage.COM on behalf of benp
Sent: Tue 02-Jan-07 20:58
To: XSI(at)Softimage.COM
Subject: shading geometry instanced to particles

hi list,

I'm using geometry instanced to particles (using the Instancing stuff in
the PType).
But i was wondering if anyone had any experience with using particle
data in the rendertree for the instance masters. Please note that  i'm
not talking about the rendertree for particle types here, just the
rendertree on the geometry i'm instancing to the particles.

scenario:
Say you had a geo of a nice little 4-leafed clover. Then you want to
instance it over a landscape using particle instancing.
The clover will only be shaded by the one shadetree, unless you have
more clovers in the instancing group each with unique shaders. This gets
limiting as you'd have to have as many geo-masters and shaders as there
are varieties of clovers.
What I'd prefer to do is have one geo master, and one master shader that
can pull out particle data (that i've written to the particle cloud)
from the instances to shade the clovers uniquely.

I don't know if this is currently limited by XSI needing a shader
written, or XSI not yet exporting the particle data to particle instances.
Does anyone have any advice??

And yes, i have tried the Particle_Color (et al)  nodes on instance
masters: No luck!
But I do get a warning from mr : "#INFO : PHEN 0.2 warn : Bad particle
raystate (00000000)" ...

tia,
benpee

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