Hi Roman,
Le 09/04/2017 à 09:23, Roman Haefeli a écrit :
Thank you, Christof and Cyrille, for your insights. I think I understood the concept. But do I need even framebuffer ping-ponging when I only _add_ to the framebuffer? Let's say I add more and more pixel-sized white squares to the buffer, I can use this as my mask, no?
Gesendet: Samstag, 08. April 2017 um 10:02 Uhr Von: "Roman Haefeli" reduzent@gmail.com An: pd-list pd-list@iem.at Betreff: Re: [PD] [Gem] Modifying single pixel of pix image
On Sam, 2017-04-08 at 08:29 +0200, Christof Ressi wrote: > > If it can be on the GPU, use a fragment shader! Do you work > with a > formula or do you set the alpha values by hand? By Hand (maybe later by a formula). Is it possible?
The idea is to have two overlaying images. The visible one slowly decomposes over time so that the image behind appears. I thought about setting alpha to for more and more pixels as a way to decompose the front image. Maybe there is another/better way?
For a "dissolve" effect I suggest creating a greyscale noise texture, and thresholding with a uniform parameter in a fragment shader, before using it as binary alpha to combine two image textures. Then you can manipulate the threshold to animate the effect.
Essentially this stores the entire history of the dissolve in a grayscale image, where the grey level determines the time of the transition for that pixel. You might want higher bit depth, or floating point, for the gray texture for a smoother effect.
Note that this does assume that the whole future/history is available in advance, if it isn't then the framebuffer methods are more appropriate.