saw this artist work and was amazed!.
British artist, Julian Beever:
Beever’s fans always describe the illusions as “amazing!” with the exclamation mark. Not a single fan has seen the drawings in person. The amazement is the technical illusion of holes in the ground and things in the air. To achieve the illusion, Beever must elongate the image across great distances of the pavement. Only in this way can the out stretched leg cut across the background of the visual field as though it was in the air, instead of drawn on the ground.
http://users.skynet.be/J.Beever/images/swim2.jpg
same drawing from different angle
http://www.artsjournal.com/aestheticgrounds/BeeverBrunellsii.JPG
http://users.skynet.be/J.Beever/images/portab3.jpg
http://users.skynet.be/J.Beever/images/dungeon.jpg
http://users.skynet.be/J.Beever/images/lobster2.jpg
click the link for more of his work