上QQ阅读APP看书，第一时间看更新

The 3D coordinate system

All 3D software uses the Cartesian coordinates system, which is made up of three-dimensional axes: the X-Axis (red), the Y-Axis (green), and the Z-Axis (blue). The exact unit size of this coordinate system is arbitrary and varies from one software package to another, but many packages set one unit on the grid to be equal to 1 meter in the real world:

There is a special type of 3D software known as Computer-Aided Design ( CAD). This is used for engineering and conforms more closely to real-life units, but for the purposes of this book, we will not be discussing CAD software.

The three-dimensional axes: X-Axis (red), Y-Axis (green), and Z-Axis (blue)

With these three axes, we can define where an object is in a 3D space using transforms. There are three types of transforms:

Location: (sometimes called translation) This determines the position of an object.
Rotation: This determines the orientation of an object.
Scale: This determines the size of an object.

Now that we understand the coordinate system, let's look at the 3D objects that will appear in the scene.