Right-handed System (Right-handed System)
By convention, OpenGL is a right-handed coordinate system. To put it simply, the positive x-axis is on your right hand side, the positive y-axis is facing upwards, and the positive z-axis is facing backwards. Imagine that your screen is in the center of the three axes, and the positive z-axis passes through your screen towards you. The coordinate system is drawn as follows:
In order to understand why it is called a right-handed coordinate system, follow the steps below:
Extend your right arm along the positive y axis and point your finger upward.
- The thumb points to the right.
- Point your index finger upward.
- The middle point is bent down 90 degrees.
If your actions are correct, then your thumb is pointing in the positive x-axis direction, your index finger is pointing in the positive y-axis direction, and your middle finger is pointing in the positive z-axis direction. If you use your left arm to do these movements, you will find that the direction of the z axis is opposite. This is called the left-handed coordinate system, and it is widely used by DirectX. Note that in the standardized device coordinate system, OpenGL actually uses the left-handed coordinate system (the projection matrix exchanges the left and right hands).
OpenGL coordinates: Note that in the standardized device coordinate system, OpenGL actually uses the left-handed coordinate system (the projection matrix exchanges the left and right hands).
The right hand department of high school mathematics:
