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

François Duchesneau sidefx at trinix.ca
Sun Jul 20 20:07:49 EDT 2008


And I've forgot to mention "Lighting Model" has to be set to "Lambert". 
Maybe other works too but the default Phong doesn't.

Michael O'Brien wrote:
> 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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>>     
>
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