Description

Feedback is a technique to mimic real-world "camera-pointed-at-screen" video feedback by grabbing an image of the current screen and using it as a background texture for subsequent frames.

The specific method used here is not particularly efficient, and special-purpose filters could accomplish all of these effects with higher levels of performance as typically needed for real-time use. However, this method is very "generic" and therefore easily tweaked, extended, adjusted, and otherwise messed with - which seems a useful quality for artistic and non-real-time uses. Have fun! :)

Updated: the code in the "effects" demo below has been updated and recompiled with Processing 0125 Beta which fixed an important memory leak with textures -- suggest you not use this code and/or general technique unless using at least 0125.

Feedback Effects Applet 256 x 256 P3D

Various types of zooms, roto-zooms and motion blurs can be accomplished by altering the scale, rotation, translation and alpha as the background texture is drawn. (These types of effects are also widely seen in the visualizations of popular music players.)

samples of various effects

And, of course, you need not limit yourself to black-and-white...

Feedback Dr. Who Applet 256 x 256 OpenGL

When performed with a real camera and screen, some sort of source signal is required to "seed" the feedback and get the process started - this can be as simple as a glint or glare on the screen cause some nearby light source, or a second camera signal, or any number of other sources mixed into the loop. When using something like "glare" as the source, the source will be fixed in place relative to the screen and only the camera moves:

Simulated Glare Applet 256 x 256 P3D

Here we must specifically create the source material (since no external sources like "glare" are imposing upon us) and with such material it is trivial to move both the camera and source material if we wish to. Also we are not limited in what that source material may consist of (for example, an image with the word "feed back" in it? :D) and quite interesting recursive figures can be produced by using the background texture also as part of the seed image:

Recursive Feedback Applet self-textured cube 256 x 256 OpenGL

By recursively texturing a number of flat quads with the feedback texture a variety of kaleidoscopic figures can be created. (analogous to how mirrors can be used in real-world camera feedback setups)

This technique was inspired and influenced by Paul Prudence's vvvv work as seen here.

Feedback Quads Applet recursive kaleidoscope 256 x 256 OpenGL

Gallery