[Sidefx-houdini-list] alpha for particles in mantra?

Michael O'Brien mobrien at pixar.com
Sun Jul 20 18:57:24 EDT 2008


Hola~

The parameter is called "Texture Tint". It doesn’t fix the issue. 

I set the geo to "Render as Points", which might be short circuiting things
a bit. When it's not set, the particle system renders as spheres. Am I
better off copying a disk onto each particle instead, and then trying to
shade the disk?

MO

--
Michael K O'Brien                               Production Engineering
Pixar                                                mobrien at pixar.com

REMY: What is that?
EMILE: I don't really know.
REMY: You don't know... and you're eating it.

> -----Original Message-----
> From: sidefx-houdini-list-bounces at sidefx.com [mailto:sidefx-houdini-list-
> bounces at sidefx.com] On Behalf Of François Duchesneau
> Sent: Sunday, July 20, 2008 4:34 PM
> To: sidefx-houdini-list at sidefx.com
> Subject: Re: [Sidefx-houdini-list] alpha for particles in mantra?
> 
> I think the Vex Decal doesn't deal with the alpha. Try the Vex Layered
> Surface and I think you've got to change the "Texture Hint" to "Diff +
> Alpha", something like that.
> 
> François
> 
> Michael O'Brien wrote:
> > Hola~
> >
> > Following the directions on the sidefx website, I was able to get a disk
> > sprite displayed in the OpenGL viewport that correctly responds to color
> and
> > alpha in GL. I created a VEX decal and a Mantra Sprite Procedural that
> are
> > read by the sprite pop.
> >
> > However, when I go to render them, alpha isn't used. I'm new to the VEX
> > language, so I might be just missing something obvious, but it looks
> like
> > alpha isn't accounted for in the decal code. Is that right? Sometimes I
> look
> > at VEX and try to read it as SL, which might be getting in the way.
> >
> > The particles have an alpha property. I setup pscale and all the mantra
> > knobs I can find to accommodate rendering transparent disks. The color
> works
> > fine, but the alpha doesn't. Any help would be appreciated.
> >
> > One thing I find interesting is that in the FX Tools both wispy smoke
> and
> > heavy smoke have rough geometric cages with shading applied to make it
> look
> > like smoke. At Pixar, we would render heavy smoke using a volumetric
> > approach and wispy smoke as using a ton of nearly transparent particles
> as
> > disks. Do people render large numbers of transparent disks in Mantra? In
> > other words, is it that my approach is wrong?
> >
> > MO
> >
> > --
> > Michael K O'Brien                               Production Engineering
> > Pixar                                                mobrien at pixar.com
> >
> > REMY: What is that?
> > EMILE: I don't really know.
> > REMY: You don't know... and you're eating it.
> >
> > _______________________________________________
> > Sidefx-houdini-list mailing list
> > Sidefx-houdini-list at sidefx.com
> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >
> >
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