From Sylvain.Pion at sophia.inria.fr Tue Nov 4 19:55:12 2003
From: Sylvain.Pion at sophia.inria.fr (Sylvain Pion)
Date: Mon Jan 9 13:41:12 2006
Subject: CGAL 3.0 Released, Computational Geometry Algorithms Library
Message-ID: <20031104195512.R1857@termite.inria.fr>
We are pleased to announce the release 3.0 of CGAL, the Computational Geometry
Algorithms Library. Version 3.0 differs from version 2.4 in licensing, in the
platforms that are supported and in functionality.
The license has been changed to either the LGPL (GNU Lesser General Public
License v2.1) or the QPL (Q Public License v1.0) depending on each package.
So CGAL remains free of use for you, if your usage meets the criteria of
these licenses, otherwise, a commercial license has to be purchased from
Geometry Factory (www.geometryfactory.com).
Major changes in this release include the following:
o Apollonius graph: the dual of the Voronoi diagram of a set of circles under
the Euclidean metric. The implementation is dynamic.
o Min_sphere_of_spheres_d: Algorithms to compute the smallest enclosing sphere
of a given set of spheres in d-dimensional space.
o Spatial Searching: Provides exact and approximate distance browsing in a set
of points in d-dimensional space (such as nearest neighbor searching).
o Largest_empty_iso_rectangle_2: Given a set of points P in the plane,
computes the largest empty iso-rectangle that are inside a given
iso-rectangle bounding box, and that do not contain any point of P.
o Interval_skip_list: A data strucure for finding all intervals in R that
contain a value, and for stabbing queries, that is for answering the
question whether a given value is contained in an interval or not.
o Existing packages have been improved in various area:
2D and 3D triangulations, Planar Maps, Arrangements...
o The CORE library (http://www.cs.nyu.edu/exact/core/) for exact computations
is now distributed as part of CGAL as well.
o We support the latest versions of the C++ compilers from GNU, Microsoft,
Intel, Sun, SGI.
o All demos are now using the portable Qt window toolkit.
See http://www.cgal.org/releases_frame.html for a complete list of changes.
The CGAL project is a collaborative effort to develop a robust,
easy-to-use, and efficient C++ software library of geometric data
structures and algorithms. The CGAL library contains:
o Basic geometric primitives such as points, vectors, lines, predicates
for testing things such as relative positions of points, and operations
such as intersections and distance calculation.
o A collection of standard data structures and geometric algorithms,
such as convex hull, (Delaunay, Regular, Constrained) triangulation, Voronoi
diagrams, planar map, arrangements, polyhedron, smallest enclosing sphere,
multidimensional query structures...
o Interfaces to other packages, e.g. for visualization, and I/O, and
other support facilities.
For further information and for downloading the library and its
documentation, please visit the CGAL web page: http://www.cgal.org/
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From jardine at uwo.ca Tue Nov 4 18:11:10 2003
From: jardine at uwo.ca (Rick Jardine)
Date: Mon Jan 9 13:41:12 2006
Subject: "Algebraic Topological Methods in Computer Science, II"
Message-ID: <3FA8320E.5060306@uwo.ca>
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Conference Announcement:
Algebraic Topological Methods in Computer Science, II
Department of Mathematics
University of Western Ontario
London, Ontario, Canada
July 16-20, 2004
This is the second installment of a conference series; the first was
held at Stanford University in the summer of 2001.
The main areas to be covered by this conference include computational
geometry and topology, networks and concurrency theory. The meeting
will consist of twenty invited lectures, with additional sessions for
shorter lectures.
The following mathematical scientists have been invited to speak:
Saugata Basu (Georgia Tech)
Marshall Bern (Xerox PARC)
Herbert Edelsbrunner (CS, Duke)
Robin Forman (Rice)
Eric Goubault (Commissariat a l'Energie Atomique, France)
Joel Hass (Math, UC Davis)
Maurice Herlihy (CS, Brown)
Kathryn Hess (Lausanne)
Michael Joswig (Berlin)
Reinhard Laubenbacher (Virginia Bioinformatics Institute)
Martin Raussen (Aalborg)
Vin de Silva (Stanford)
Michael Stillman (Cornell)
This conference has been funded by grants from the National Science
Foundation and the Fields Institute.
All conference announcements and information will be available at the
web page http://www.math.uwo.ca/~jardine/at-csII.html.
The organizers for this meeting are:
Gunnar Carlsson, gunnar@math.stanford.edu
Rick Jardine, jardine@uwo.ca
From scot at moosilauke.cs.dartmouth.edu Wed Nov 12 13:11:37 2003
From: scot at moosilauke.cs.dartmouth.edu (Scot Drysdale)
Date: Mon Jan 9 13:41:12 2006
Subject: Tenure-track positions at Dartmouth
Message-ID: <200311121811.hACIBb616865@moosilauke.cs.dartmouth.edu>
Please note that algorithms (including Computational Geometry) is an
area which we are targeting in these searches.
Scot Drysdale
===========================================
DARTMOUTH COLLEGE
Faculty Position in Computer Science
The Department of Computer Science seeks candidates for faculty positions
starting in September 2004. We anticipate several tenure-track openings
at the Assistant Professor level. Senior faculty appointments may also
be possible.
Candidates in programming languages/compilers, security, systems,
graphics, algorithms, robotics, and computational science are particularly
encouraged to apply. Strong candidates in all areas of computer science
will be seriously considered.
Persons interested should submit a curriculum vitae, a research statement,
and a teaching statement. Please ask at least four professionals to send
letters of reference, at least one of whom can comment on teaching. Full
consideration will be given to applications that arrive by December 1, 2003.
Please send application materials and general inquiries to:
Delia Mauceli
Computer Science Recruiting
Department of Computer Science
Dartmouth College
6211 Sudikoff Laboratory
Hanover, NH 03755-3510
Specific questions can be referred to Scot Drysdale, at
recruit@cs.dartmouth.edu.
Information on faculty and their research, facilities, and graduate students
is available at http://www.cs.dartmouth.edu. Our department is affiliated
with the Institute for Security Technology Studies, and further information
can be found at http://www.ists.dartmouth.edu.
Dartmouth is an equal opportunity/affirmative action employer and encourages
applications from women and members of minority groups.
-------------
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From thill at tomotherapy.com Wed Nov 12 08:59:37 2003
From: thill at tomotherapy.com (Ted Hill)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
Message-ID: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
I want to be able to calculate the area inside a closed many-sided
polygon.
Given an array of the (x,y) vertices that define the polygon, is there a
well-known algorithm that can calculate the enclosed area quickly?
Thanks,
Ted Hill
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From andreas.fabri at geometryfactory.com Wed Nov 12 23:27:12 2003
From: andreas.fabri at geometryfactory.com (Andreas Fabri)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
In-Reply-To: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
References: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
Message-ID: <3FB2B3C0.60203@geometryfactory.com>
Hi,
You might have a look at CGAL, the Computational Geometry Algorithm Library.
http://www.cgal.org/Manual/doc_html/basic_lib/Polygon_ref/Function_area_2.html#Cross_link_anchor_0
andreas
Ted Hill a ?crit:
> I want to be able to calculate the area inside a closed many-sided
> polygon.
>
>
>
> Given an array of the (x,y) vertices that define the polygon, is there
> a well-known algorithm that can calculate the enclosed area quickly?
>
>
>
> Thanks,
>
>
>
> Ted Hill
>
>
>
>
>
>
>
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From barequet at cs.technion.ac.il Thu Nov 13 00:07:59 2003
From: barequet at cs.technion.ac.il (Gill Barequet)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
Message-ID: <200311122207.hACM7xNU012260@csa.cs.technion.ac.il>
On Wed, 12 Nov 2003 08:59:37 "Ted Hill" wrote:
> I want to be able to calculate the area inside a closed many-sided polygon.
> Given an array of the (x,y) vertices that define the polygon, is there a
> well-known algorithm that can calculate the enclosed area quickly?
Use the well-known sailor's algorithm: Assume wlog that the polygon is above
the X axis. Project all the polygon's edges to the X axis, and sum up the
signed areas of all the induced trapezoids. (Set the sign of a trapezoid
acoording to whether or not the inducing oriented edge goes from left to right.)
(Theoretically you can compute the area in linear time also by triangulating
the polygon and summing up the areas of the triangles... 8-)
Gill
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From hans at tat.physik.uni-tuebingen.de Thu Nov 13 00:17:42 2003
From: hans at tat.physik.uni-tuebingen.de (Torsten Hans)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
In-Reply-To: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
Message-ID:
Hi,
a very elegant and fast (since it is linear) way to do this is
to use Green's theorem over the border of the closed polygon.
the polygon doesn't need to be convex.
Just as a reminder: Green's theorem reduces a surface integral
to a line integral over the border of the surface integral.
(sorry for my bad english).
here is a c code fragmet that calculates the area
and center.
num_vertices is the number of vertices of the polygon.
v2dx[] and v2dy[] are double arrays that store the x and y positions.
for easier computation the first vertex v2dx[0] and v2dy[0]
is stored in v2dx[n] and v2dy[n] again.
-------------------------------------------------------
double area = 0;
double center2dx = 0;
double center2dy = 0;
for (int i=0; i I want to be able to calculate the area inside a closed many-sided
> polygon.
>
> Given an array of the (x,y) vertices that define the polygon, is there a
> well-known algorithm that can calculate the enclosed area quickly?
>
> Thanks,
>
> Ted Hill
>
>
>
>
-------------
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From hans at tat.physik.uni-tuebingen.de Thu Nov 13 00:20:08 2003
From: hans at tat.physik.uni-tuebingen.de (Torsten Hans)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
In-Reply-To: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
Message-ID:
Hi again,
in my previous post I said I used Green's theorem.
This is not correct, i meant Stoke's theorem.
sorry for that.
Torsten Hans
On Wed, 12 Nov 2003, Ted Hill wrote:
> I want to be able to calculate the area inside a closed many-sided
> polygon.
>
> Given an array of the (x,y) vertices that define the polygon, is there a
> well-known algorithm that can calculate the enclosed area quickly?
>
> Thanks,
>
> Ted Hill
>
>
>
>
-------------
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From skoranne at tanner.com Wed Nov 12 14:55:17 2003
From: skoranne at tanner.com (Sandeep Koranne)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
Message-ID: <9F874F181B17D511A6BE00B0D0AB3303012FCE81@shelby.tanner.com>
Hi TEd,
Here is a simple method,
let us say the polygon is given by { (0,0), (10,0), (10,10), (0,10) }
Gven the array of [x,y] write then in 2 columns
X Y
--------
0 0
10 0
10 10
0 10
0 0
do cross multiplication as you march down the column and sum the results on
left side and right side
eg
0*0 + 10*10+10*10+0*0 = 200 on left column
0*10+ 0*10 +10*0 + 10*0 = 0 on right column
subtract the left column from right column = 0 - 200 = -200
divide this by 2 to get area = -100 (if you want absolute area use abs)
HTH
sandeep
btw: this can be programmed in 4way SIMD on Intel and others to run
"extremely fast"
-----Original Message-----
From: Ted Hill [mailto:thill@tomotherapy.com]
Sent: Wednesday, November 12, 2003 7:00 AM
To: compgeom-discuss@research.bell-labs.com
Subject: Algorithm for Area of a closed polygon.
I want to be able to calculate the area inside a closed many-sided polygon.
Given an array of the (x,y) vertices that define the polygon, is there a
well-known algorithm that can calculate the enclosed area quickly?
Thanks,
Ted Hill
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From Jeffrey_Danowitz at amat.com Thu Nov 13 11:44:36 2003
From: Jeffrey_Danowitz at amat.com (Jeffrey_Danowitz@amat.com)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
Message-ID:
Hi!
Perhaps this is equivalent to Gill's idea. Pick any vertex on the polygon.
No need to assume anything except that the array, p, of vertices is in
polygonal order, which it usually the case. From that point, build 2
vectors (p(b),p(b+1)), (p(b),p(b+2)) and take half the cross product
(signed area). Continue around taking vectors (p(b),p(b+i)) and
(p(b),p(b+i+1)) i=2,...n-1, summing the signed areas as you go along.
In the end take the absolute value -- and this is the area.
If you think about it, this is just Green's theorem in action. Clearly
this is a linear algorithm.
I hope my description is clear.
Yours,
Jeff
Gill Barequet
11/13/2003 12:07 AM
To: compgeom-discuss@research.bell-labs.com, thill@tomotherapy.com
cc:
Subject: Re: Algorithm for Area of a closed polygon.
On Wed, 12 Nov 2003 08:59:37 "Ted Hill" wrote:
> I want to be able to calculate the area inside a closed many-sided
polygon.
> Given an array of the (x,y) vertices that define the polygon, is there a
> well-known algorithm that can calculate the enclosed area quickly?
Use the well-known sailor's algorithm: Assume wlog that the polygon is
above
the X axis. Project all the polygon's edges to the X axis, and sum up the
signed areas of all the induced trapezoids. (Set the sign of a trapezoid
acoording to whether or not the inducing oriented edge goes from left to
right.)
(Theoretically you can compute the area in linear time also by
triangulating
the polygon and summing up the areas of the triangles... 8-)
Gill
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From dnave at psc.edu Wed Nov 12 21:23:16 2003
From: dnave at psc.edu (Demian M. Nave)
Date: Mon Jan 9 13:41:12 2006
Subject: Algorithm for Area of a closed polygon.
In-Reply-To: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
References: <1E2E66102E75104D8C740340EBCD98671BC279@tomoex.tomotherapy.com>
Message-ID:
Hi Ted,
> I want to be able to calculate the area inside a closed many-sided
> polygon.
As long as your polygon has no self-crossings or internal holes, this
algorithm is probably the simplest. It will return twice the _signed_ area
of your polygon:
Let 'vertices' be an array of N pairs (x,y), indexed from 0
Let 'area' = 0.0
for i = 0 to N-1, do
Let j = (i+1) mod N
Let area = area + vertices[i].x * vertices[j].y
Let area = area - vertices[i].y * vertices[j].x
end for
Return 'area'
If the vertices of your polygon are specified in counter-clockwise order
(i.e. by the right-hand rule), then the area will be positive. Otherwise,
the area will be negative, assuming the polygon has non-zero area to begin
with.
Hope this helps. Send another note to the mailing list if not. :-)
Cheers,
Demian
--
Demian M. Nave | dnave@psc.edu | Ph 412 268-4574
Pgh. Supercomputing Center | www.psc.edu/~dnave | Fx 412 268-8200
4400 Fifth Avenue | "When your work speaks for itself, don't
Pittsburgh, PA 15213 | interrupt." - Kanin
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From jjjjcrack at yahoo.com.cn Fri Nov 14 00:39:52 2003
From: jjjjcrack at yahoo.com.cn (=?gb2312?q?f=20f?=)
Date: Mon Jan 9 13:41:12 2006
Subject: Ask for help
Message-ID: <20031113163952.35575.qmail@web15202.mail.bjs.yahoo.com>
Dear Sirs:
who can tell me the process of contributing papers
to computer & Graphics. The email address, the
contacter, and so on.
Thank you very much!
Ding jian(jjjjcrack@yahoo.com.cn)
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
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From grima at us.es Thu Nov 20 16:53:52 2003
From: grima at us.es (Clara I. Grima)
Date: Mon Jan 9 13:41:12 2006
Subject: [Ewcg04] EWCG'04: SECOND ANNOUNCEMENT
In-Reply-To:
Message-ID: <000001c3af7e$8148d540$66b193c1@subdireccion>
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_______________________________________________
Ewcg04 mailing list
Ewcg04@listas.us.es
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From pesasa at utu.fi Mon Nov 24 11:34:45 2003
From: pesasa at utu.fi (Petri Salmela)
Date: Mon Jan 9 13:41:12 2006
Subject: ICALP'04 - Call for Papers
Message-ID:
Printable pdf-version at:
http://www.math.utu.fi/icalp04/icalp-call.pdf
___________________________________________________________________
CALL FOR PAPERS - ICALP'04
31st International Colloquium on
Automata, Languages and Programming
July 12-16, 2004, Turku, Finland
http://www.math.utu.fi/icalp04/
___________________________________________________________________
The 31st International Colloquium on Automata, Languages and
Programming sponsored by the European Association of Theoretical
Computer Science will take pl