NAME

       gfill_area  - output primitive for filling polygonal areas.

SYNOPSIS

       #include <ncarg/gks.h>

       void gfill_area(const Gpoint_list *point_list);

DESCRIPTION

       point_list.num_points
                   (Gint, Input) - The number of points in the polygon to be filled.  Must be greater than two.

       point_list.points
                   (Gpoint *, Input) - The X and Y world coordinates of the polygon.

USAGE

       The  area  to  be filled is delimited by the sequence of straight line segments connecting the successive
       points                         ((point_list.points[0].x,                         point_list.points[0].y),
       ...(point_list.points[point_list.num_points-1].x, point_list.points[point_list.num_points-1].y)) The last
       point  in the polygon is connected to the first point with a straight line segment in the case that it is
       not the same as the first point.

       Given a polygon whose edges cross each other, it becomes ambiguous as to what constitutes the "inside" of
       the polygon.  The algorithm used in GKS is as follows: for a given point, draw a  ray  starting  at  that
       point  and  going  to  infinity  in any direction; if the number of intersections between the ray and the
       polygon is odd, the point is within the polygon, otherwise it is outside.  If the  straight  line  passes
       through  a polygon vertex tangentially, the intersection count is not affected.  If a point is within the
       polygon, it is included in the area to be filled.

       Several interior styles (hollow, solid, and various hatch patterns) can be selected.  See the  man  pages
       for gset_fill_int_style and gset_fill_style_ind for these.

       Note  well:  By default in GKS, the interior fill style is hollow, or no fill. If you call gfill_area and
       do not get a filled interior as you expected, you will probably need to call gset_fill_int_style  to  set
       the fill style to something other than "hollow".

ACCESS

       To use the GKS C-binding routines, load the ncarg_gks and ncarg_c libraries.

SEE ALSO

       Online:       gset_fill_int_style(3NCARG),       gset_fill_style_ind(3NCARG),      gset_colr_rep(3NCARG),
       gset_fill_colr_ind(3NCARG),   ginq_fill_int_style(3NCARG),   ginq_fill_style_ind(3NCARG),    gks(3NCARG),
       ncarg_gks_cbind(3NCARG)

       Hardcopy: User's Guide for NCAR GKS-0A Graphics; 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                                               March 1993                                 GFILL_AREA(3NCARG)