Re: shading geometry instanced to particles

["Graham D Clark" <mailgrahamdclark(at)gmail.com>]

yeah this is a popular problem, for hair instancing I had similar issue a couple weeks ago. similar to the workaround you guys came up with for particles halfy suggested using screen space coordinates to differentiate them, which is good for projected moblur but not for differentiating them and having the texture stick...

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Graham D Clark
http://www.CafeFx.com
http://www.grahamdclark.com
http://www.linkedin.com/pub/1/173/498

 

On 1/2/07, benp <benp(at)rsp.com.au> wrote:

thanks for the answer halfy, makes sense.
out of curiosity, has this been a popular problem at all?

i guess i'll have to use my freakn brain to get around this one for the
moment :P
benpee

Halfdan Ingvarsson wrote:
> 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
>
> ------------------------------------------------------------------------
> *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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