[PD] Crossfade between 4 films moving a slider

[chris clepper]

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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