       SippSpotLightOpening light opening
              Modify  the  opening  angle  of  the lightcone of a
              spotlight.  Opening is the  opening  angle  of  the
              lightcone. The cone defined will be completely lit,
              a soft edged lightcone will start to blend out out-
              side this angle.  If the number is prefixed with an
              "R", then it is taken as radians, if it is prefixed
              with "D", then it is taken as radians.  If not pre-
              fix, then degrees is assumed.
