Cans of spray paint with two nozzles, slightly offset from each other, one spraying red paint, one blue. The paint would have to be quick drying and semi-translucent. If the graffitist keeps their hand level, then the end result would be two identical, overlapping images, in red and blue respectively. To the unititiated, the graffiti tags would make no sense, but pedestrians "in the know" could wear their stylish 3-D glasses at all times; and enjoy the illusion of seeing three-dimensional drawings float all around them, as they walk down the street.-- DrWorm, Oct 16 2009 3D chalk http://www.youtube....watch?v=-Xy6oxbNWHc [jaksplat, Oct 16 2009] 4 in 1 4_20in_201_20aerosol_20sprays [po, Oct 16 2009] Anagraffiti?-- phoenix, Oct 16 2009 //slightly offset from each other// - this would not give a 3D impression. At the very best, if the colors where somehow mutually translucent (something i do not see happening), the graffiti would seem to be on a plane parallel to the wall, either in or out, but in the picture itself, everything would be co-planar. You'd need to be able to vary the distance for that (possibly not impossible, Dalí is said to have done some 3D painting free-hand (though i doubt it, probably was using a viewer at the time of painting))-- loonquawl, Oct 16 2009 Yesss! This is a brilliant idea!! To get 3-D, all you would need is to have the two nozzles separated by a small distance and angled *away* from eachother. Then, you can control the apparent depth of the 3D image by moving your hand closer to, or further from, the wall.
With your hand far away from the wall (ie, close to yourself), the two colours will be widely separated, giving the stereoscopic illusion of being close to you (ie, in the foreground). With your hand closer to the wall (further from yourself), the two colours will be closer together (or superimposed), giving the illusion of being further away.
In other words, the apparent depth of the image would reflect your hand position in 3D. This is an excellent idea! [+], and would that I had more buns to give.-- MaxwellBuchanan, Oct 16 2009 Trouble is I think graffiti artists control the fineness of their line by varying the distance from the wall - close is sharp, far is fuzzy. Perhaps a 2-handed thing with a lazy-tong style linkage that intuitively adjusts the seperation?-- pocmloc, Oct 16 2009 What [Max] said. [+]
To address the sharpness issue, the nozzles could be fitted with widgets similar to those you find on the end of a garden hose, which allow you to adjust the output between a single, straight stream and a finely diffused mist.-- Wrongfellow, Oct 16 2009 ... and do so automatically to compensate for the nozzle's distance from the wall in spray direction, as measured by a built-in infrared laser distance measure.-- jutta, Oct 16 2009 That's far too technical a solution. Good idea.-- MaxwellBuchanan, Oct 16 2009 random, halfbakery