Movie with a mask?

[Graham]

On Wed, 16 Jul 2003 00:52:16 -0700, Richard Gaskin 
<ambassador at fourthworld.com> wrote:


>Peterson Trethewey wrote:
>
> > I need to play a movie with a mask, like a clip
> > region, or an alpha channel.  I figured out how to do
> > this sort of thing with a picture, but movies are
> > totally different.  Is it possible to tell a player to
> > do this?
>
>Yes: set the alwaysbuffer of the player to true, then lay any masked image
>over the player.

But what if the movie requires a different mask per frame? - imagine for 
example a windmill going round, so that the sails are in a different 
position in each frame, and you want the user to see the background behind 
the windmill except where the sails happen to be. Then AFAIKS you have to 
have a kind of movie mask - is this perhaps an alpha channel for the movie? 
I have tried to understand this in QT Pro but have got precisely nowhere. 
Information about how to do this sort of thing (including whether it's even 
possible) seems to me very hard to come by. My current solution is to avoid 
the problem by replacing the windmill with a spinning disk, but I would 
rather not.

Graham


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Graham Samuel / The Living Fossil Co. / UK & France