In real life, we can tell where objects are by measuring distance between them. As for
placing them, moving them, and keeping track of where they are nature has developed
a pretty good system. On the computer though, we have to somehow keep track of
objects in a 3D scene. Mathematicians have developed the coordinate system. You
have probably learned in geometry about the X and the Y axis. Well, these two axis
define a coordinate plane, that is, a two dimentional world. However, to work in three
dimentions, we need one more axis, the Z axis....