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@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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