Defines a viewing transformation by giving the viewing position and the coordinates of a reference point in the scene.
view_xx-coordinate for the viewing position
view_yy-coordinate for the viewing position
view_zz-coordinate for the viewing position
reference_xx-coordinate for the reference point
reference_yy-coordinate for the reference point
reference_zz-coordinate for the reference point
twistControls the rotation along with viewer's z axis.