I am finally getting back into visuals and I am just getting my feet wet with GEM. I used to use visual jockey gold, which is really great for freeware but man that thing was a pain in the tukus sometimes! All kind of stupid glitches and menu options that weren't controllable by MIDI. GEM on linux is the way to go for me.

I'm trying to get an old algorithm to work on gem that involves video feedback. Basically I start off with some video to initiate the loop, then I chromakey the video, apply filters/ color effects/ zoom rotation etc to the output and feed it back into the background of the chroma-keyed image. This makes it so that cutout portions of the video that I am playing go crazy with rainbow color goopy nonsense. Here's an example:

(notice the video staggering and crappy resolution due to vj gold :/ )

So far I have found this page ( http://www.hellocatfood.com/feedback-loops-in-pure-data/ ) which details using the pix_snap object to capture the entire render window and spit it into a texture. That works fine except that in this example the texture is being applied to a 3D object and I just want to use it for a plane, at least to start off with.

I am having some difficulty getting this method to work just printing to a single plane. Before I go shooting in the dark on how to fix it has anyone else figured out how to do this already/ have some resources for me to find? Google shows me a lot of people who have done it but very few who share their code.

Thanks!

no time to test, but try taking a [rectangle] objekt instead of [sphere] and [cube]

Ok so I have made an example patch of what I want to do. I am basically trying to chroma key the background of my video to alpha so that I can put the feedback as a texture to another rectangle in the background. Basically I am doing this because when I was printing everything to the same rectangle with [pix_snap] I was getting some weird shrinking of the feedback channel but also because I want to be able to do effects with the 3d rendering.

My problem is that I only seem to be getting black in the background of the chroma keyed film. If you look I am using the alpha object and then I have a white cube in the background of the image (being rendered before the chromakeyed image.) Logically I should be able to see the white cube in the holes left in the chromakeyed image but all I get is black. The spigot at the bottom of the patch will turn of the film so that you can see the rectangle in the back.

http://www.pdpatchrepo.info/hurleur/first_feedback_test.pd

If you use [pix_alpha] you can achieve the effect you're looking for.