3D paintings....worth a look

have u ever heard of 3D images. Most of you must have seen emails regarding it. But its a real art. I always got astonished and stops at every image for few minutes to see how it is made. Just have a look at these video links. These are some of the worlds best 3D paintings.
http://www.youtube.com/watch?v=A6oNm13rtfw
http://www.youtube.com/watch?v=tkfKh0vSySg
The links below are the most amazing one:
http://www.youtube.com/watch?v=J2nqulPloIc
http://www.impactlab.com/2006/03/09/amazing-3d-sidewalk-art-photos/

Some best one: