Adding an extra dimension

The pictures here are simply amazing.

Viewed from the proper angle, they look completely 3 dimensional and astonishingly real (especially look at the last one).

Perspective is a hard thing to get right (and not just in Art). While travelling around Europe, I was struck by how long it took Italian artists to come to terms with using perspective while painting. A lot of the artists were sculptors who also dabbled in the painting arts so it makes sense that it would be a struggle to go from can-get-your-hands-around-it to a flat piece of canvas.