class TGLPerspectiveCamera: public TGLCamera

 Construct default XOZ perspective camera

 Construct perspective camera

 Destroy perspective camera

 Setup camera limits suitible to view the world volume defined by 'box'
 and call Reset() to initialise camera.

 Reset the camera to defaults - reframe the world volume established in Setup()
 in default state. Note: limits defined in Setup() are not adjusted.

 Zoom the camera - 'adjust lens focal length, retaining camera position'.
 Arguments are:

 'delta' - mouse viewport delta (pixels) - +ive zoom in, -ive zoom out
 'mod1' / 'mod2' - sensitivity modifiers - see TGLCamera::AdjustAndClampVal()

 Returns kTRUE is redraw required (camera change), kFALSE otherwise.

 Truck the camera - 'move camera parallel to film plane'.
 Returns kTRUE is redraw required (camera change), kFALSE otherwise.

 Apply the camera to the current GL context, setting the viewport, projection
 and modelview matricies. After this verticies etc can be directly entered
 in the world frame. This also updates the cached frustum values, enabling
 all the projection, overlap tests etc defined in TGLCamera to be used.

 Arguments are:
 'box' - view volume box - used to adjust near/far clipping
 'pickRect' - optional picking rect. If non-null, restrict drawing to this
 viewport rect.

 Configure the camera state.
   fov     - set directly field-of-view in degrees (default = 30);
   dolly   - additional move along the camera forward direction;
   center  - new camera center (can be 0 for no change);
   hRotate - additional "up/down" rotation in radians;
   vRotate - additional "left/right" rotation in radians.