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vfx
07-08-2003, 11:45 PM
Hi all,

I was watching a making of today, and in typical style, there was no explanation as to how in combustion you extract an alpha of smoke on a black background, or to separate water splashes onto a separte layer from its black background. Does anyone know how to achieve this effectively? Is it done in the similar way as keying from bluescreen? If so what about the slightly transparent areas of smoke which would surely be lost in the proccess of extraction.

Please advice.

gmask
07-08-2003, 11:47 PM
A luma key would be one way to do orr simple add the luminance of the image to itself as alpha.

This is probably the most basic way to composite two images and is sort of like how a double exposure works.
You can also compsoite somehtign liek this but using add or an additive blend mode like in After Effects..

vfx
07-09-2003, 01:02 AM
Thnx anyone else any ideas

gmask
07-09-2003, 01:25 AM
Originally posted by vfx
Thnx anyone else any ideas

I think I have covered all the practical ways to do this.. I'm just not familair with combustion... but surely it has a luma keyer, a way to set luminance as a matter and an additive mode.

Chris
07-09-2003, 10:35 AM
yup, you can use the discreet keyer (set on 'luma') the set matte operator, & its got all the usual transfer modes. Those are the best ways to do it alright...

public
07-09-2003, 04:01 PM
Bringing the smoke layer into combustion adn simply setting it's transfer mode to screen works pretty well.

1armedScissor
07-11-2003, 04:07 AM
you can also duplicate the layer and use one of them as a luma stencil for the other layer or a set matte operator, add your favourite colour correction operator to the stencil layer/set matte layer and tweak to achieve the desired effect.

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