The angles and for the left and right eyes are measured counterclockwise from the line to the distractor to the line to the fixate, shown in degrees. The difference between these angles is the important "binocular disparity" used in static visual depth perception and described in the Demonstration "Binocular Disparity (Visual Depth Perception 7)" (see Related Links).

The node points of the eyes, shown as green dots in the eyes, are at the location of the effective "pinhole lens" created by a combination of the focal properties of the cornea and the eye's lens. The location of the node point determines the relation between the internal and external angles and , and and for this simple model that assumes the cross sections of the eyes are circles. On the slider, this location is given as a fraction of the radius of the eye. When the node percent is zero the internal and external angles are equal, but a more typical physiological approximation would be a node percent equal to 1/2.

The other sliders are self-explanatory: if you move them, you will see what they do.