Sciography

Sciography, or sciagraphy, is a term for the graphical technique of depicting shadows on objects, or cast by objects. It is often used to create an illusion of depth in a two-dimensional image, particularly in architectural drawing. The term comes from the Greek σκιά "shadow" and γράφειν graphein, "write".
In general sciography, the light source is imagined as the sun inclined at 45 degrees to both the vertical plane and the horizontal plane coming from the left hand side. The resultant shadow is then 'projected' onto an adjacent surface in the drawing.