The graphics pipeline can apply three possible transformations to an entity:
- The entity's block transformations
- The viewport's view transformation
- The perspective transformation (if perspective is enabled from DVIEW)
Each transformation produces a new type of coordinates, as shown in the following figure. If not in perspective mode, eye and display coordinates are identical.
For the REGEN, HIDE, and SHADE commands, the entity's world coordinates are sent through the graphics pipeline shown in the figure above. The view transformation specifies a particular view of the world coordinates, analogous to viewing a scene with a camera. The camera has a location in world space and a particular orientation toward the world coordinate “scene.” When the view transformation is complete, world coordinates are transformed to eye coordinates, looking down the Z axis of the camera.
If perspective is enabled, the eye coordinates are transformed to display coordinates. This transformation involves division according to how far away something is from the camera, so that objects farther away from the camera appear smaller than objects closer to the camera.
The following sections discuss these coordinate systems in greater detail.