There are currently several 3D GIFs on Tumblr using depth of field and graphic elements to achieve their effect. Some of these 3D optical illusion pictures are really good, but the effect was already known to many classic painters.

The white lines define the plane where the screen is, creating a mental division between background, mid-plane and foreground. Combined with the camera’s depth of field blur, it tricks our brain into thinking that things are popping out of the screen.