[PD] Crossfade between 4 films moving a slider

[Nuno Godinho]

Hi Chris,

Thank you for your thorough instructions! I still didn't finish it but it's
on it way to working quite well. 

In my particular case tweaking the alpha directly is much better than using
pix_mix because this way the films can be dealt with independent (in
paralel) instead of cascading pix_mix objects.

Bye,
Nuno

> -----Original Message-----
> From: cgclepper at gmail.com [mailto:cgclepper at gmail.com] On 
> Behalf Of chris clepper
> Sent: sexta-feira, 9 de Dezembro de 2005 4:28
> To: Nuno Godinho
> Cc: pd-list at iem.at
> Subject: Re: [PD] Crossfade between 4 films moving a slider
> 
> pix_mix does the most basic mixing possible: (imageA * 
> coeffA) + (imageB * coeffB).  It does not touch the alpha 
> channel at all.
> 
> If you want to do 'alpha' blending in hardware then use the 
> [alpha] object followed by [colorRGB 1 1 1 0.5] and feed the 
> alpha coefficients into the right inlet.  Of course the 
> images have to overlap and be drawn in the proper order for 
> this to work.
> 
> I made a tutorial comparing the two methods here:
> http://taproot.dyndns.org/~cgc/tutorial_gem/tutorial8.html
> 
> cgc
> 
> On 12/8/05, Nuno Godinho <eu at nunogodinho.com> wrote:
> > Hi there,
> >
> > Using a MIDI slider (0-127) I have to crossfade between 4 films 
> > separated by regions. When the slider is between 0-30 film A is 
> > displayed, when it moves from 30 to 31 it quickly 
> crossfades to film 
> > B, then at 60/61 crossfades to film C and finally at 90/91 
> crossfades to film D.
> >
> > I was building this making use of three cascading pix_mix. 
> But then I 
> > figured if it wouldn't be simpler to, instead of cascading, 
> play with 
> > pix_alpha on each picture independently and thus creating 
> my own crossfade.
> > This way I would get more control over each film and build 
> something 
> > more modular. The idea is: when the fader moves from 30 to 31 I use 
> > pix_alpha to make film A disappear at the same time making film B 
> > appear. Do you think this is a good approach?
> >
> > How is crossfade built anyway? How is pix_mix implemented? By using 
> > alpha channel, right?
> >
> > Any better ideas?
> >
> > Thanks in advance,
> > Nuno
> >
> >
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