PERSPECTIVE

        [GREG2\]PERSPECTIVE [Altitude  Azimuth]  [/FACTOR  Fv  Ov]  [/LOWER]
    [/LINES]  [/STEP Nsx Nsy] [/AXES Xmin Xmax Ymin Ymax] [/CENTER] [/VERTI-
    CAL Vmin Vmax]

    Makes a parallel projective view of the Regular Grid array, with  hidden
    lines  removed.  If  /LINES option is present, lines along a single axis
    are plotted. Altitude and Azimuth are the values  of  the  corresponding
    viewing  angles  in  Degrees. Default values are 30 and 45 at the begin-
    ning, and then the last values given. The upper part  is  drawn,  unless
    the /LOWER option is present.

    Automatic scaling to match approximately the current box is used, but it
    is only a rough guess and may fail if extrema of the Regular Grid occurs
    near  the edges. Fine tuning of the plot scale can be obtained using the
    /FACTOR option. It controls scaling of the Regular Grid  values  by  the
    factor  Fv (default 1) and an offset Ov which is in physical units along
    the Y direction of the plot.

    The Regular Grid array is plotted according to the  orientation  implied
    by  command LIMITS, but the whole array is plotted. The /STEP option may
    be used to indicate to take only 1 pixel over Nsx ones for  the  X  axis
    (resp.  Nsy and Y). The /AXES option plots (X,Y) axes. The /VERTICAL op-
    tion controls the max, min of plotted perspective and plots  a  Z  axis.
    The /CENTER option centers the perspective. BLANKED PIXELS are forced to
    the minimum value of the map, or the Vmin value when the  /VERTICAL  op-
    tion is in use.