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SETPVI

       SUBROUTINE  SETPVI (VINDEX,MAXVTX,NVERTX)
 C$    (Set Polygon Vertex Indices)
 C$    Set the  polygon vertex  indices.  These  are color  lookup
 C$    table indices for each polygon vertex which are to be  used
 C$    for filling  polygons  of  interior  style  "shaded".   The
 C$    shading is  done in  a two  step process.   First the  edge
 C$    values are  determined by  linear interpolation  along  the
 C$    edges using the  vertex values.  Then  the interior  values
 C$    are determined by  linear interpolation from  edge to  edge
 C$    along the scan lines that cover the interior of the polygon
 C$    image.  The arguments are:
 C$
 C$    VINDEX(*).........Array  of  polygon  vertex  color  lookup
 C$                      table indices to  be used for  subsequent
 C$                      polygons.
 C$    MAXVTX............Actual declared dimension of VINDEX(*).
 C$    NVERTX............Number   of   vertex   entries  currently
 C$                      present in VINDEX(*).
 C$
 C$    Note that  the facility  offered by  this routine  is  only
 C$    available on  rather sophisticated  (and expensive)  raster
 C$    display devices, and  cannot be  conveniently simulated  on
 C$    non-raster display  devices.  No  warning is  given if  the
 C$    selected  display  device  cannot   support  it,  and   the
 C$    operation requested will simply be ignored.
 C$    (27-JAN-82)