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<http://www.cs.man.ac.uk/~amurta/software/index.html#gpc>/ | /gpctool
<http://www.cs.man.ac.uk/~amurta/software/index.html#gpctool>/ |
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News and developments
/Updated 29 July 2003/
* 29 July 03: GEORGE/DREW MCLEAN, we tried to reply to your email
enquiry but the mail to you bounced. Please contact us again.
* Stefan Schedel <mailto:Stefan.Schedel@loewe.de> has produced a
Delphi/Pascal port of gpc v2.30. You can download it here
<ftp://ftp.cs.man.ac.uk/pub/toby/gpc/gpc.pas.gz>.
* Joerg Raedler has made available his Python bindings
<http://www.dezentral.de/soft/Polygon/> to GPC.
* A new email account has now been set up for library related
enquiries: gpc@cs.man.ac.uk <mailto:gpc@cs.man.ac.uk>
* Release 2.31 of the /gpc/ library is now available. See the
version information
<http://www.cs.man.ac.uk/~amurta/software/VERSIONS.TXT> for details.
* A /gpc/ library graphical evaluation package
<http://www.cs.man.ac.uk/~amurta/software/index.html#gpctool> is
also available for Unix / X11 users.
Users may also be interested to know that the GNU MAVERIK
<http://aig.cs.man.ac.uk/systems/Maverik/> VR System, developed by the
University of Manchester Advanced Interfaces Group
<http://aig.cs.man.ac.uk> has now been released under the GNU General
Public License.
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A general polygon clipper library (gpc)
/Release 2.31/
A flexible and highly robust polygon set operations library for use with
C applications, as referenced in the comp.graphics.algorithms FAQ
<http://www.cis.ohio-state.edu/hypertext/faq/usenet/graphics/algorithms-faq/faq.html>
and the UIUC Computational Geometry Pages
<http://compgeom.cs.uiuc.edu/~jeffe/compgeom/>. The /gpc/ library is
estimated to have thousands of users worldwide, and is subject to
several hundred downloads each month.
This software is free for non-commercial use. Anyone wishing to use the
/gpc/ library in support of a commercial product please email
gpc@cs.man.ac.uk <mailto:gpc@cs.man.ac.uk>.
/Difference, intersection, exclusive-or and and union operations./
Features
Difference, intersection, exclusive-or and union clip operations are
supported.
Polygons may be comprised of multiple disjoint contours.
Contour vertices may be given in any order - clockwise or anticlockwise.
Contours may be convex, concave or self-intersecting.
Contours may be nested (i.e. polygons may have holes).
Output may take the form of either polygon contours or tristrips.
Hole and external contours are differentiated in the result.
Coincident edges and degenerate regions are handled correctly.
Performance
The current release (v2.31) of /gpc /is faster than older releases (e.g.
v2.22). The following tables give performance results measured on a 650
MHz Athlon, running GNU/Linux and compiled using gcc.
Test 1 is the "British Isles map" example shown above. The subject
polygon has 2 contours totalling 1857 edges, while the clip polygon has
4 contours totalling 28 vertices.
Difference
Intersection
Exclusive-or
Union
*gpc v2.22*
54
67
46
54
*gpc v2.31*
63
67
61
63
*Table 1: *Clip operations per second for Test 1.
Test 2 is an example consisting of 54 small rectangular contours with
many overlapping regions and coincident edges. The subject and clip
polygons each have 27 contours comprising 108 edges.
Difference
Intersection
Exclusive-or
Union
*gpc v2.22*
1616
1787
1386
1392
*gpc v2.31*
1929
2868
1540
1542
*Table 2: *Clip operations per second for Test 2.
Click here <ftp://ftp.cs.man.ac.uk/pub/toby/gpc/tests.tar.Z> to download
the test examples..
Downloading gpc
The clipper library sources are available either as a Unix compressed
tarfile (28k) <ftp://ftp.cs.man.ac.uk/pub/toby/gpc/gpc231.tar.Z> or a PC
Zip file (15k) <ftp://ftp.cs.man.ac.uk/pub/toby/gpc/gpc231.zip>.
On-line documentation
<http://www.cs.man.ac.uk/~amurta/software/gpc.html> for the /gpc/
library.
Version information
<http://www.cs.man.ac.uk/~amurta/software/VERSIONS.TXT>.
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A graphical polygon clipper evaluation package (gpctool)
/Release 1.01/
<http://www.cs.man.ac.uk/~amurta/software/gpctool.gif>
(Click to enlarge)
The /gpctool/ package allows the interactive graphical evaluation of the
/gpc/ polygon library under Unix / X11. Compilation requires Mesa
<http://www.mesa3d.org/> (or OpenGL <http://www.opengl.org/>) and xforms
<http://world.std.com/~xforms/> libraries - no precompiled binaries are
available.
Downloading gpctool
The sources are available as either a Unix compressed tarfile (62k)
<ftp://ftp.cs.man.ac.uk/pub/toby/gpc/gpct101.tar.Z> or a PC Zip file
(38k) <ftp://ftp.cs.man.ac.uk/pub/toby/gpc/gpct101.zip>.
*Note:* This software is completely unsupported.
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Links
Related polygon clipping links
<http://www.cs.man.ac.uk/~amurta/software/links.html>.
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/Alan Murta <http://www.cs.man.ac.uk/~amurta/index.html>/
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