View Full Version : Urgent help needed regarding alphas and mattes

05 May 2003, 05:12 PM

Here is my situation. I have two scene elements, a robot in the background and a group of people approaching the robot. The robot has its own alpha generated from a 3D program to mask it out from the live action background. At this point the robot is cut out over the foreground of the people in the live action plate, while i want him behind the people. I have created an alpha matte for t he people in Mokey, and was wondering how I plug this alpha footage into my order of operations in Combustion.. meaning, how I add it to the footage of my robot so that the live action people are masked from it. I'm completely lost!

I would appreciate any help!

05 May 2003, 09:26 PM
I'm assuming Mokey has generated a grayscale matte to use to mask out the people? If thats the case, import the image sequence that mokey generated, then either set it as the stencil layer for your robot layer, or assign a 'set matte' operator to your robot & use the matte footage as the source.

Milo FX
05 May 2003, 12:48 AM
If I understand correctly, you have got a principal photograpy that contain some people approaching a robot (that will produce separately in a 3d application). And you prepared a garbage matte for the people that rest front of the robot.
So import your principal photography without a matte channel as a first layer of your composite. Than import your robot layer with robo layer matte and finally reimport your principal photography layer with a garbage matte channel as a third layer. That way robo layer will rest beetween the principal photograpy background and the people approaching...
I hope this help...

05 May 2003, 12:51 AM
Thanks milo and chris.. but how do you import something as a garbage matte?

Also, the set matte operator seems to nullify the robots original alpha :-(

Thanks again guys

05 May 2003, 04:02 AM
Where do I find the stencil operator? Can't seem to locate it anywhere.

Thanks again :-)

05 May 2003, 08:26 AM
you will find the stencil operator in the composite the surface button,its in there

06 June 2003, 03:06 AM
if you wanted to add the mattes together as one you could import your robot footage and render only the alpha, then do a new composite of your robots alpha plus you grabage matte alpha, render that, then import it back into the original comp and use the set matte operator

06 June 2003, 08:24 AM

Import both clips (matte and footage :surprised ), select the footage to be matted and go to composite controls, select "layer" open the Stencial Layer dropdown and select the matte configure it to alpha or luma and voila!

I hope that helps!
See Ya! :thumbsup:

06 June 2003, 08:28 AM
Thanks everyone, works nicely!

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