The OpenGL coordinate system refers to the series of transformations that convert 3D object coordinates into a 2D image on the screen. Here’s a breakdown of how these coordinates are handled in OpenGL:
1. **Object Coordinates (Model Coordinates)**: These are the coordinates relative to the object's local origin. This system is used for defining the shape and structure of objects in a scene.
2. **World Coordinates**: This is the coordinate system of the entire scene. After applying model transformations (translation, rotation, and scaling), the object coordinates are transformed into world coordinates, placing the object within the larger scene.
3. **View Coordinates (Camera Coordinates)**: The view transformation converts world coordinates into view coordinates, which represent the scene from the camera’s perspective. This transformation accounts for the camera’s position and orientation.
4. **Clip Coordinates**: The projection transformation (either perspective or orthographic) converts view coordinates into clip coordinates. This step determines how the scene is projected onto a 2D plane, preparing it for the next stage.
5. **Normalized Device Coordinates (NDC)**: After clipping, the coordinates are transformed into NDC, where they are mapped to a normalized cube with coordinates ranging from -1 to 1 in each axis.
6. **Window Coordinates**: Finally, NDC coordinates are mapped to window or screen coordinates based on the viewport dimensions and resolution, where they are translated into pixel positions on the display.
Each transformation stage in this pipeline helps in rendering a 3D scene correctly on a 2D display by converting and normalizing the coordinates through a series of steps.
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