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Old 09-05-2004, 04:48 PM   #1
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Lukasz Przybytek
Compositor/CG Generalist
United Kingdom
Join Date: Jun 2004
Posts: 387
xsi smoke: alpha channel ?

hi there!
ive "recreated" xsi smoke shader by using the constant density node and plugging it to the volume channel of the material. i used sample scene that someone at xsibase forum has prepared. it looks great (with a white background)... but i cant get it to work, so it renders out with nice alpha channel.
my newbie thoughts are that there should be some way to plug the density channel as a alpha/transparency.
for the surface channel i have velvet thingy...
when i render this out and lets say turn off primary rays on the background... my smoke renders as solid white in alpha.

ummm ohhh... any thoughts?
hope you understand my problem.

thanks a lot for any ideas.

take care,
Old 09-06-2004, 06:42 AM   #2
Facial Deluxe
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Posts: 2,179
I'm not an expert with particles but, are you using a 2D background color ?
it looks great (with a white background)...
If so remove it, 2D background color fills the alpha whatever your setting (at least in my case).
You are a pluggin.
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Old 09-06-2004, 06:50 AM   #3
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Jason Dexter
Lighting/Rendering/Pipeline TD
Providence, USA
Join Date: Jan 2003
Posts: 6,594
You can do some tricks in post as a last resort... render your smoke as you need it... then render a second version with a bright constant background (blue, red or green) like a green screen... then through channel manipulation do a key to extract your alpha.
(Sans Gerfuffle)

On a VFX Hiatus
Old 09-06-2004, 11:44 AM   #4
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Lukasz Przybytek
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United Kingdom
Join Date: Jun 2004
Posts: 387
im not using particles for the smoke effect. just loft surface with the proper shader.

you gave me some idea on how to achieve what i want. will have to test it out today.

thank you for your help guys

Old 01-19-2006, 05:00 AM   #5
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