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Name: PGPOLY

Purpose: draw a polygon, using fill-area attributes

Category: GRAPHICS

File: pgplot.src

Author: T.J. Pearson

Use: see description below.

Description:

SUBROUTINE PGPOLY (N, XPTS, YPTS)
INTEGER N
REAL XPTS(*), YPTS(*)

Fill-area primitive routine: shade the interior of a closed
polygon in the current window. The action of this routine depends
on the setting of the Fill-Area Style attribute (see PGSFS).
The polygon is clipped at the edge of the
window. The pen position is changed to (XPTS(1),YPTS(1)) in world
coordinates (if N > 1). If the polygon is not convex, a point is
assumed to lie inside the polygon if a straight line drawn to
infinity intersects and odd number of the polygon's edges.

Arguments:
N (input) : number of points defining the polygon; the
line consists of N straight-line segments,
joining points 1 to 2, 2 to 3,... N-1 to N, N to 1.
N should be greater than 2 (if it is 2 or less,
nothing will be drawn).
XPTS (input) : world x-coordinates of the vertices.
YPTS (input) : world y-coordinates of the vertices.
Note: the dimension of arrays XPTS and YPTS must be
greater than or equal to N.

Updates: Oct 16, 1998: JPT automatically extracted from source.