Tip 15: PhotoModeler’s Camera Frustum View
PhotoModeler’s 3D Viewer is a great tool for viewing your 3D model, as well as viewing the positions of the camera(s) that took the photos. A new feature in 2012.1.1 now shows the camera frustums as well. A frustum is the volume the camera sees, shown graphically by a 3D wireframe solid. These are useful to determine overlap and to view the relationships of the view volumes.
The http://en.wikipedia.org/wiki/Viewing_frustum describes it further.