[my advanced OpenGL learning journey] learning notes of OpenGL coordinate system

I'm learning OpenGL When , We must learn about coordinate changes , But in fact, I don't learn well , Many times I feel very confused , Learn again today OpenGL The coordinate system of , Collect the information on the Internet and organize this note .

One 、OpenGL Coordinate change

OpenGL The device screen that eventually renders the graphics to is essentially 2D Of , The process of rendering a graph is to 3D The scene is transformed into the final 2D Process of scenario .

OpenGl The points defined in the user construct the local coordinate system of the model , The model is transformed into the world coordinate system , Then it is transformed into camera coordinate system through visual transformation , Then it is transformed into clipping coordinate system through projection transformation , Then the perspective division is converted to the normalized equipment coordinate system (NDC), Finally, it is mapped to the screen coordinate system through viewport transformation .

The coordinate transformation process is shown in the following figure ：

The above figure depicts the detailed process of object transformation from local object coordinate system to screen coordinate system , Give me a list OpenGL The coordinate system in .

• World Coordinates（ World coordinate system ）
• Object Coordinates( Object coordinate system 、 Model coordinate system 、 Local coordinate system or current drawing coordinate system )
• Eye Coordinates( Eye coordinate system or camera coordinate system )
• Clip Coordinates( Crop coordinate system )
• Normalized Device Coordinates (NDC) ( Normalized equipment coordinate system )
• Window Coordinates (Scr