3D art is easy to do.
At left is a picture of a design created using red and green clay on white cardboard. The original design is three dimensional but the picture is flat.
Below are two more pictures of the same design, but with the camera moved horizontally first right, then left of center. If you cross your eyes while looking at the dual images, such that they overlap in the center, you will see the image in a simple form of 3D.
This is easy to do with any form of camera (including a cell phone): Simply take two pictures of the same scene, one while standing a few inches right of center, and the other a few inches left. Put the images side by side and voila!
(Click picture for higher resolution image)