3D Graphics Programming with QuickDraw 3D 1.5.4

View Plane Cameras

Labels

ASCII: ViewPlaneCamera
Binary: vwpl ( = 0x7677706C )

Data Format



 
Float32             viewPlane

Float32             halfWidthAtViewPlane

Float32             halfHeightatViewPlane

Float32             centerXOnViewPlane

Float32             centerYOnViewPlane

viewPlane: The distance from the camera location to the view plane.
halfWidthAtViewPlane: One half the width of the view plane window.
halfHeightAtViewPlane: The value in the halfWidthAtViewPlane field divided by the horizontal-to-vertical aspect ratio of the view port. The value in this field determines the half-height of the view plane window.
centerXOnViewPlane: The x coordinate of the center of the view plane window, specified in the view plane coordinate system.
centerYOnViewPlane: The y coordinate of the center of the view plane window, specified in the view plane coordinate system.

Data Size

Description

A view plane camera is a type of perspective camera defined in terms of an arbitrary view plane. The camera vector is normal to the view plane, and the distance from the camera location to the view plane is measured in the direction defined by the camera vector. The window on the view plane and its center are defined in the projection plane coordinate system determined by the camera's camera placement object. The view volume of a view plane camera is determined by the four rays through the camera location and through the four corners of the rectangular window on the view plane, together with the two clipping planes. The view volume is the frustum whose top is the rectangle having as its vertices the intersections of these four rays with the near clipping plane and whose base is the rectangle having as its vertices the intersections of these rays with the far clipping plane.

The center of projection of a view plane camera is the camera location point. If the center of the window defined by a view plane camera is not at the origin of the view plane, then the camera yields an off-axis view. The projection determined by a view plane camera may have one, two, or three principal vanishing points.

A view plane camera may be used to obtain a close-up image of a single object by using the approximate center and dimensions of that object to specify the size and location of the window on the view plane.

Parent Hierarchy

Shared, shape, camera.

Parent Objects

View hints (sometimes).

Child Objects

Camera placement, camera view port, camera range (optional). If a camera does not have one of these child objects, then it should be assigned the default values specified in the section on that child object.

Example



 
Container (

    ViewPlaneCamera (

        20

        15.0

        15.0

        18

        29

    )

    CameraPlacement ( ... )

    CameraRange ( ... )

    CameraViewPort ( ... )

)