Perspective

Creating a notion of movement in space.

Alhazen - a mathematician Arab, around 1000AD first understood perspective properly. Previously the Greeks thought light went from the eyes to an object. Alhazen realised they were fucking wrong. That we see an object because each point of it directs and reflects a ray of light into the eye.

The Greek view could not explain how an object, like my hand, seems to change size when it moves. In Alhazen's account it's clear that the cone of rays that comes from the outline and shape of my hand grows narrower as I move my hand away from you. As I move it towards you, the cone of rays that enters your eye becomes larger and subtends a larger angle.

The Music of the Spheres;

In a fresco of the city of Florence (around AD1350) the painter has shown the view of the city, around buildings, over a wall, etc as if the city were arranged in tiers.

"But this is not a matter of skill; it is a matter of intention. There is no attempt at perspective because the painter thought of himself as recording things, not as they look, but as they are: 

A God's eye view, a map of eternal truth."

The perspective painter has a different intention. The picture and it's inhabitants are mobile. He deliberately makes us step away from any absolute and abstract view. A point of view in time, more than in space.