The most basic visual
entity is the point. The point has no size, but it has a location.
To determine the location
of points, we first establish an arbitrary point in space as the
We can then say a point’s
location is so many units left (or right) of the origin, so many
units up (or down) from the origin, and so many units higher (or
lower) than the origin.
These three numbers give
us the 3D coordinates of the point in space. For example, a point
7 units right (x), 4 units down (z), and 3 units above (y) the origin
has the XYZ coordinates (7,4,3).
To specify points on
the opposite side of the origin, we use negative numbers. In the
example, a point at (-5, -2, -1) would be 5 units left of the origin,
2 units up, and 1 unit below.
In computer graphics,
we don’t really say the point is “left/right”, “up/down”, or “higher/lower”.
Instead we call the three dimensions the X axis, the Z axis, and
the Y axis.
Y-up and Z-up
and visual effects, the tradition is to use Y as the “up” or elevation
axis, with X and Z as the “ground” axes. However, some other industries traditionally
use Z as the up axis and X and Y as the ground axes.
Maya lets you switch
the up axis between Y and Z. Select
> Settings/Preferences > Preferences,
then click Settings in the list on the left.