Defines a viewing transformation by giving the viewing position and the coordinates of a reference point in the scene.
view_x
x-coordinate for the viewing position
view_y
y-coordinate for the viewing position
view_z
z-coordinate for the viewing position
reference_x
x-coordinate for the reference point
reference_y
y-coordinate for the reference point
reference_z
z-coordinate for the reference point
twist
Controls the rotation along with viewer's z axis.