Viewing with Computers (OpenGL)

We can now return to three-dimension? , graphics from a computer perspective. Because viewing in computer graphics is based on the synthetic-camera model, we should be able to construct any of the classical views. However, there is a fundamental difference. All the classical views were based on a particular relationship among the objects, the viewer, and the projectors. In computer graphics, we stress the independence of the object specifications and camera parameters.
In terms of the pipeline architecture, viewing consists of two fundamental operations. First, we must position and orient the camera. This operation is the job of the model-view transformation. After vertices pass through this transformation, they are represented in eye or camera coordinates. The second step is the application of the projection transformation.
OpenGL starts with the camera at the origin of the object frame, pointing in the negative z-direction. This camera is set up for orthogonal views and has a viewing volume that is a cube, centered at the origin and with sides of length 2. The default projection plane is the plane z = 0 and the direction of the projection is along the z-axis. Thus, objects within this box are visible and projected. . . . . . . . . . . . . . . . . . . . . . .