3D Graphics Programming with QuickDraw 3D 1.5.4

View Plane Cameras

A view plane camera is a type of perspective camera defined in terms of an arbitrary view plane. In general, you'll use a view plane camera to create a perspective image of a specific object in a scene. The view plane camera is the only type of perspective camera provided by QuickDraw 3D that allows off-axis viewing (that is, viewing where the center of the projected object on the view plane is not on the camera vector), which is convenient when scrolling an image up or down, or left to right.

The view frustum associated with a view plane camera is determined by a view plane (located at a specified distance from the camera) and the rectangular cross section of an object, as shown in Figure 10 . The point at which the camera vector intersects the view plane defines the origin of the view plane coordinate system. You specify a rectangular cross section of an object by specifying its center (in the view plane coordinate system) and the half-width and half-height of the cross section. In Figure 10 , the center of the cross section is the point ( c x , c y ), and the half-width and half-height are the distances d x and d y , respectively.

Figure 10 A view plane camera

See "View Plane Camera Data Structure" for complete details on the data you need to provide to define a view plane camera. See "Managing View Plane Cameras" for a description of the routines you can use to create and manipulate view plane cameras.