[PD] noob question: alpha channel multiplication

[Roman Haefeli]

hi michal

using [pix_alpha] works, but it will eat much of your cpu.  otoh [colorRGB] 
, which also is able to render the alpha-channel, is calculated on the 
graphicscards processor.  in order to process also the alpha-channel, you 
need to put an [alpha]-object into the chain. once you have a picture, where 
only the person is visible, you can apply this texture on as many geos (e.g 
[square] or [rectangle] etc.) as you want.

roman


----- Original Message ----- 
From: "michal panaak" <panaak at gmail.com>
To: <pd-list at iem.at>
Sent: Monday, June 05, 2006 3:02 PM
Subject: [PD] noob question: alpha channel multiplication


> hi pd people!
>
> i'm working on this project:
>
> the basic idea is to create an interactive installation, where anyone 
> could move around with a bluescreen behind his back, while in front of 
> him, there would be a projection screen with a huge crowd of clones of 
> oneself facing the performer..
>
> i need to capture a person in front of a bluescreen, create alpha channel 
> of the person, multiply it and import it into a picture (for example a 
> picture of some plaza) so that it would look like a regiment of clones 
> moving around in a grid.. in perspective..
>
> i think i'd need functions pix_alpha / pix_chroma_key / pix_mask for the 
> alpha channel processing.. and then some other GEM functions to multiply 
> it and create a grid inside a picture.. but i'm not sure exactly how..
>
> all i ask is to kick me in the right direction..
>
> -mp-
>
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