A virtual camera and lens system in a three dimensional computer graphic
modeling environment is set using a nominal focal length and a focus
distance. A true focal length is calculated. An optical axis object that
represents the optical axis of the virtual camera and lens system is
created in the three dimensional computer graphic modeling environment.
An object is attached to the optical axis at a location that visualizes
the setting of the virtual camera and lens system as determined from the
true focal length. The focal length of the virtual camera and lens system
is set to the calculated true focal length. The focus distance and f-stop
may be determined from near and far focus points.