/*
   *  The placement of the camera.
   */
  
  struct TQ3CameraPlacement {
      TQ3Point3D                      cameraLocation;             /*  Location point of the camera  */
      TQ3Point3D                      pointOfInterest;            /*  Point of interest           */
      TQ3Vector3D                     upVector;                   /*  "up" vector             */
  };
  typedef struct TQ3CameraPlacement       TQ3CameraPlacement;
  /*
   *  The range of the camera.
   */
  
  struct TQ3CameraRange {
      float                           hither;                     /*  Hither plane, measured from "from" towards "to"   */
      float                           yon;                        /*  Yon  plane, measured from "from" towards "to"     */
  };
  typedef struct TQ3CameraRange           TQ3CameraRange;
  /*
   *  Viewport specification.  Origin is (-1, 1), and corresponds to the 
   *  upper left-hand corner; width and height maximum is (2.0, 2.0),
   *  corresponding to the lower left-hand corner of the window.  The
   *  TQ3Viewport specifies a part of the viewPlane that gets displayed 
   *  on the window that is to be drawn.
   *  Normally, it is set with an origin of (-1.0, 1.0), and a width and
   *  height of both 2.0, specifying that the entire window is to be
   *  drawn.  If, for example, an exposure event of the window exposed
   *  the right half of the window, you would set the origin to (0, 1),
   *  and the width and height to (1.0) and (2.0), respectively.
   *
   */
  
  struct TQ3CameraViewPort {
      TQ3Point2D                      origin;
      float                           width;
      float                           height;
  };
  typedef struct TQ3CameraViewPort        TQ3CameraViewPort;
  
  struct TQ3CameraData {
      TQ3CameraPlacement              placement;
      TQ3CameraRange                  range;
      TQ3CameraViewPort               viewPort;
  };
  typedef struct TQ3CameraData            TQ3CameraData;
  /*
   *  An orthographic camera.
   *
   *  The lens characteristics are set with the dimensions of a
   *  rectangular viewPort in the frame of the camera.
   */
  
  struct TQ3OrthographicCameraData {
      TQ3CameraData                   cameraData;
      float                           left;
      float                           top;
      float                           right;
      float                           bottom;
  };
  typedef struct TQ3OrthographicCameraData TQ3OrthographicCameraData;
  /*
   *  A perspective camera specified in terms of an arbitrary view plane.
   *
   *  This is most useful when setting the camera to look at a particular
   *  object.  The viewPlane is set to distance from the camera to the object.
   *  The halfWidth is set to half the width of the cross section of the object,
   *  and the halfHeight equal to the halfWidth divided by the aspect ratio
   *  of the viewPort.
   * 
   *  This is the only perspective camera with specifications for off-axis
   *  viewing, which is desirable for scrolling.
   */
  
  struct TQ3ViewPlaneCameraData {
      TQ3CameraData                   cameraData;
      float                           viewPlane;
      float                           halfWidthAtViewPlane;
      float                           halfHeightAtViewPlane;
      float                           centerXOnViewPlane;
      float                           centerYOnViewPlane;
  };
  typedef struct TQ3ViewPlaneCameraData   TQ3ViewPlaneCameraData;
  /*
   *  A view angle aspect camera is a perspective camera specified in 
   *  terms of the minimum view angle and the aspect ratio of X to Y.
   *
   */
  
  struct TQ3ViewAngleAspectCameraData {
      TQ3CameraData                   cameraData;
      float                           fov;
      float                           aspectRatioXToY;
  };
  typedef struct TQ3ViewAngleAspectCameraData TQ3ViewAngleAspectCameraData;