drawings/shadows    

Shadows are created automatically any time a light shines. They are so inevitable that we would actually notice their absence more than we notice their presence.  A shadow image can be seen as a drawing, as it describes a 3D situation in 2D format, as seen from a particular viewpoint  - the position of the light source.  Unlike a traditional drawing, each depicted object continually creates its own image - which has no physical substance and can be created instantly or destroyed without trace.