.TH Polypack 3NCARG "March 1995" UNIX "NCAR GRAPHICS"
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.SH NAME
Polypack - a set of routines allowing polygons to be manipulated in various
ways. Each of the six principal routines is given a "clip" polygon, a "subject"
polygon, and a workspace; it operates on the two polygons in some way to create
either a derivative polygon or a set of trapezoids representing the interior
of that derivative polygon and then passes these on to a user-specified
processing routine.
.SH SYNOPSIS
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PPDIPO - generates and returns the boundary of the "difference" polygon, which
consists of all points that are inside the subject polygon but not inside the
clip polygon.
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PPINPO - generates and returns the boundary of the "intersection" polygon,
which consists of all points that are inside both the clip polygon and the
subject polygon.
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PPUNPO - generates and returns the boundary of the "union" polygon, which
consists of all points that are inside either or both of the clip polygon
and the subject polygon.
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PPDITR - generates and returns a set of trapezoids representing the
interior of the "difference" polygon, which consists of all points that
are inside the subject polygon but not inside the clip polygon.
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PPINTR - generates and returns a set of trapezoids representing the
interior of the "intersection" polygon, which consists of all points
that are inside both the clip polygon and the subject polygon.
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PPUNTR - generates and returns a set of trapezoids representing the
interior of the "union" polygon, which consists of all points
that are inside either or both of the clip polygon and the subject polygon.
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PPPPAP - can be called to preprocess a polygon in such a way as to remove
certain peculiarities that can cause minor cosmetic errors in the output
from the routines that return trapezoids.
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PPPLCL - clips a polyline against a clipping rectangle. It is intended that,
eventually, there should be a better routine that will clip a polyline
against an arbitrary polygon, but that routine has not yet been written.
.SH C-BINDING SYNOPSIS
#include <ncarg/ncargC.h>
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c_ppdipo
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c_ppditr
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c_ppinpo
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c_ppintr
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c_ppplcl
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c_ppppap
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c_ppunpo
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c_ppuntr
.SH ACCESS
To use Polypack routines, load the NCAR Graphics libraries ncarg, ncarg_gks,
and ncarg_c, preferably in that order.  
.SH MESSAGES
None.  All error conditions in Polypack routines are reported by means
of an error-flag argument.
.SH SEE ALSO
Online:
ppdipo, ppditr, ppinpo, ppintr, ppplcl, ppppap, ppunpo, ppuntr,
ncarg_cbind.
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Hardcopy:
None.
.SH COPYRIGHT
Copyright (C) 1987-2009
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University Corporation for Atmospheric Research
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The use of this Software is governed by a License Agreement.