You've heard of it, maybe seen it, be it in real life or online. I like it very much, looks like alot of thought put into the actual making of it, everything has to be the right angle and length. Wonder if the rain washed it away.. Some use paint some use atualy chalk. (probably lots of chalk)
This site discusses 5 of the, according to them, most talented 3d chalk artists, I paticularly like the first one they mentioned, Edgar Mueller, and the last one, Kurt wenner.
This video is from Julian Beever, a transformers 3d sidewalk project.
And this one is from Edgar Mueller, showing the progress of how it is made, and also random people being funny.
Also, there's a book about pavement art, available at Amazon.com, Click here to go to amazon