generally this should be the semi-diameter of the surface. What "normalized" implies that the maximum is scaled to 1 and the rest of the cooridnates are calculated as a ratio.. This is similar to Normalized Coordinates used for pupil interception. See the Normalized Field/Pupil Coorindates in the user manual. HiZ*+T.B
uXn1
'K<'2
Hope this helps ..