What is a Gnomon?
Our Jantar Mantars which were built in 18th century by Maharaja Jai Singh II in 5 cities viz. in Delhi, Jaipur, Ujjain, Mathura and Varanasi are actually Huge Gnomons.
Today a 3D gnomon is commonly used in CAD and computer graphics. This 3D Gnomon aids to positioning objects in the virtual world. By convention, the X axis direction is colored red, the Y axis green and the Z axis blue.