Understanding 3D Coordinate Systems in OpenGL

There are two alignments in which 3D coordinates can be defined: the left-handed system and the right-handed system. Each is used to define the direction in which rotations around the axes occur and can be visualized using the thumb and first two fingers on the respective hands (see Figure 4.11). For both systems, the thumb is used to represent the z axis; the direction in which the fingers wrap into a fist is the direction of a positive rotation:

Figure 4.11: The right-hand and left-hand rules of 3D axis orientation

For a detailed elucidation, you are encouraged to read the following web page:

https://en.wikipedia.org/wiki/Right-hand_rule

In OpenGL, eye coordinates are defined using the right-handed system, meaning that the positive z axis protrudes out of the screen (toward the eye) whereas traditionally in DirectX, the z axis is positive in the opposite direction. Other 3D software packages seem to have...