ok! in fact I saw GIFs made to reproduce this effect before but it only works in motion, right ?

the motion is for the benefit of the people that can't bend their eyes and refocus enough to see static depth .. simulated motion is relatively headache free at least : )

I started a wiki page for Tom's 3D filter which describes some of the settings but it definitely needs more added:
http://sourceforge.net/p/gmic/wiki/2D%2 ... onversion/

The quality of the 3D effect will depend heavily on the type of picture used and settings in the filter, overall it's one of the most tricky effects to use. I have my own simplified version under testing > garagecoder but it still needs work. If you're having trouble seeing the 3D effect have a look at some "real" anaglyphs created using two cameras (search for "3D anaglyph") - the depth perception is usually a lot stronger.

I have an entire deviantArt Gallery full of 'red/cyan 3D images I created using the G'Mic plugin.

If you create a depth-map of the image and load that into G'Mic's 3D conversion plugin, with just the default setting you can create a pretty good red/cyan 3D image. Of course you do need a pair of 3D glasses to view the 3D effect though.

Have you guys checked out the new script on the registry named "COLOGRAM.SCM "
http://registry.gimp.org/node/28059
I have fixed the script so it shows in the menus as Filters>Cologram
It creates a 3D image like this.

More information here - http://medienkunstonline.de/indexen.html
Things you will need to start - http://medienkunstonline.de/3dprinten.html

That script is for the printing stage assuming you've already prepared two or more layers with appropriate viewpoint offsets. It's a neat idea to print onto slide transparencies and position behind a simple grating, thanks for sharing.