NAME

       STUMSL - This routine is the user-definable external subroutine used to draw masked streamlines. The
       default version of the routine draws any polyline all of whose area identifiers are greater than or equal
       to zero.

SYNOPSIS

       CALL STUMSL (XCS,YCS,NCS,IAI,IAG,NAI)

DESCRIPTION

       XCS         (REAL  array,  assumed  size  NCS,  input): Array of X coordinates of the points defining the
                   polyline with the given set of area identifiers.

       YCS         (REAL array, assumed size NCS, input): Array of Y coordinates  of  the  points  defining  the
                   polyline with the given set of area identifiers.

       NCS         (INTEGER,  input):  Number  of points; assumed size of the X and Y coordinate arrays, XCS and
                   YCS.

       IAI         (INTEGER array, assumed size NAI,  input):  Array  of  area  identifier  values.  Each  value
                   represents  the  area  identifier with respect to the area group in the area group array with
                   the same array index.

       IAG         (INTEGER array, assumed size NAI, input): Array of area- identifier groups.

       NAI         (INTEGER, input): Number of area  identifier  groups.  The  current  version  of  Streamlines
                   supports up to 64 area groups.

USAGE

       ´STUMSL´  is  the  name  given to the default version of the masked streamline drawing routine, and it is
       also the name given to the argument through which the external subroutine is passed to STREAM.   However,
       you  may  choose  any acceptable FORTRAN identifier as the name of a user-defined version of the routine.
       The substitute routine must have an argument list equivalent to the default  version  of  STUMSL.   Also,
       whether  or  not the default version is used, the subroutine that calls STREAM should contain an external
       declaration of the routine, such as:

                 EXTERNAL STUMSL

       If the MSK parameter is greater than 0, signifying that masking is to be performed, Streamlines sends one
       or more sets of X and Y polyline coordinate  arrays  to  the  area  masking  routine,  ARDRLN,  for  each
       streamline.  ARDRLN subdivides the polyline into pieces such that each smaller polyline has a single area
       identifier with respect to each area identifier group, then makes a call  to  STUMSL  for  each  polyline
       piece.  While  the  default  version  of  STUMSL only checks to see that none of the area identifiers are
       negative, a user-defined version could perform more complicated decision processing based on knowledge of
       the meaning of specific area identifier groups and/or area identifier values. Note that, before  invoking
       STUMSL, ARDRLN modifies the user coordinate space by making the following calls:

               CALL GETSET(VPL,VPR,VPB,VPT,WDL,WDR,WDB,WDT,LLG) CALL SET(VPL,VPR,VPB,VPT,VPL,VPR,VPB,VPT,1)

       These  calls  temporarily turn the user to NDC mapping into an identity, allowing the user to call any of
       the routines, CURVE, CURVED, or the GKS routine GPL, to render the polygon piece without worrying about a
       possible non-identity mapping between user and world coordinates.

       The current version of Streamlines supports masked drawing with up to 64 area  groups.  Streamlines  will
       exit with an error message if an area map with more than 64 groups is passed to it.

ACCESS

       To use STUMSL, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.

SEE ALSO

       Online:  stgetc, stgeti, stgetr, stinit, stream, streamlines, streamlines_params, strset, stsetc, stseti,
       stsetr, stuixy, stumta, stumxy, ncarg_cbind.

       Hardcopy: NCAR Graphics Fundamentals, UNIX Version

COPYRIGHT

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.

UNIX                                               April 1993                                     STUMSL(3NCARG)