One of the most important operation that the GM has to perform is the modification of the view volume frustum with respect to the viewing system adopted by the ROV camera. The viewing system type is given by the height angle and the aspect ratio, that is the result of the width angle divided by the height angle. The GM gives the possibilty of changing the width and the height angles with the View Volume Editor, that is a dialog window composed of:
- a 3D graphical viewer, to show the view volume frustum;
- an height angle and a width angle thumbwheel widgets, to change the frustum dimentions;
- a near and a far plane scale widgets, to change the distances of the near plane and the far plane of the viewing frustum from the viewpoint.
The 3D graphical viewer is responsible to show the viewing frustum from an external viewpoint. The viewing frustum is shown as a transparent shape with the starting point coincident with the currently selected viewpoint in order to represent the correct position and orientation of the view volume clipping planes. The user is able to navigate through the scene as an external viewpoint and to see how the environment primitives are managed with respect to frustum dimentions.