Conference Report: 11th ACM Symposium on Computational Geometry
On 4 - 7 June 1995 the University of British Columbia in Vancouver,
BC, Canada, hosted the 11th ACM Symposium on Computational Geometry
(SCG), which is jointly sponsored by SIGGRAPH and SIGACT. 156
registrants attended, including 50 students. With the exception of
the cold windy weather for the outdoor salmon barbeque, the conference
went smoothly. (The salmon itself was excellent.)
The program consisted of 3 invited speakers, 41 technical papers, 6
videos in the fourth annual Video Review, and, a new feature this
year, 18 two-page communications that were presented as posters or
demos at the conference. Also new for this year were conference
T-shirts: they showed the breadth of application of geometric
computation by displaying two dozen figures from accepted papers and
communications.
INVITED SPEAKERS
The 1995 SCG had an all-California slate of invited speakers: Michael
Goodchild, head of the NCGIA and professor of Geography at UC Santa
Barbara spoke on current trends and challenges in Geographic
Information Systems (GIS). (Several attendees wanted to discuss how
Computational Geometry could or was attempting to meet his challenges;
he, unfortunately, had to leave soon after his talk.) David Haussler,
from the Department of Information and Computation at UC Santa Cruz,
gave a (mostly) non-geometric talk entitled "Prediction, Data
Compression, and Metric Dimension." Pat Hanrahan, who was at
Princeton when he was invited but moved to Stanford shortly
afterwards, spoke on "Geometric Algorithms and the Rendering
Equation." He deserves special thanks for participating in the entire
conference.
PAPERS
Emo Welzl (FU Berlin), the conference program chair, encouraged
theoretical, expiremental, and applied papers. The program committe
selected 41 out of 107 submissions. The full program is available on WWW.
This report summarizes the mathematical and applied themes, such as
basic geometric objects: convex polytopes, Voronoi diagrams,
arrangements, and shortest paths; basic geometric operations:
searching, counting, optimization, and theorem proving; and
applications to robotics, GIS, and graphics.
-
Work in these areas ranges from theoretical to the applied, and
sometimes mixes the two. To take "convex polytopes" as an example:
Gritzmann & Hufnagel (U Trier) give a theoretical answer to the
"Minkowski reconstruction" problem that arises in computer vision,
Chan (UBC) gives simple and beautiful algorithms for 2-D and 3-D
output-sensitive convex hull computation as a result of general
theoretical work, and Avis & Bremner (McGill) give an insightful study
of convex hull algorithm performance, especially for degenerate
inputs.
- Voronoi diagrams are studied for curves by Alt (FU Berlin) &
Schwarzkopf (Utrecht), for polygonal distance functions by Abellanas,
Hernandez (U Poli. Madrid), Klein (FernU Hagen), Neumann-Lara (U Nac.
Aut. Mexico), Urrutia (U Ottawa) and for polyhedral distance functions
by Boissonnat, Yvinec (INRIA), Sharir & Tagansky (Tel Aviv) Related is
a study of Delaunay triangulation algorithms in the plane Su
(Transarc) & Drysdale (Dartmouth); Minimum-weight and other
triangulations are also studied by Dickerson, Montague (Middlebury) &
McElfresh (Dartmouth) and by Aichholzer, Aurenhammer, Taschwer & Rote
(Technische U Graz).
- Arrangements continue to be a fruitful area of study for bounds on
substructure complexity, Tagansky (Tel Aviv); on envelopes, Agarwal
(Duke), Schwarzkopf (Utrecht) & Sharir (Tel Aviv); and on levels,
Agarwal (Duke), Efrat & Sharir (Tel Aviv). Also considered is robust
implementation by Guibas (Stanford) & Marimont (Xerox PARC).
- Shortest path variations are studied: precision-sensitive in 3D by
Choi, Yap (Courant) & Sellen (Saarlandes); network approximations by
Mata & Mitchell (SUNY SB); approximate path queries among rectangles
by Chen, Klenk (Notre Dame) & Tu (Taiwan), paths among rectangular
prisms in 3D, Choi & Yap (Courant).
- New and improved data structures and algorithms for geometric
searching problems are given for closest pair maintenance,
Bespamyatnikh (Ural State); rectangle enclosure and point-dominance,
Gupta, Janardan, Dasgupta (Minn) & Smid (MPI Inf), and approximate
range searching Arya (MPI Inf) & Mount (UMD). Arya (MPI Inf), Mount
(UMD), and Narayan (Harvard) also tried to analyze
boundary effects in nearest neighbor search structures.
- Combinatorial work includes exciting lower bounds for Hopcroft's
problem by Erickson (UC Berkeley), Helly-type theorems by Matousek
(Prague), progress on Conway's thrackle conjecture by Lovasz (Yale),
Pach (Courant) & Szegedy (AT&T Bell Labs), cutting pseudo-parabolas
by Tamaki & Tokuyama (IBM Tokyo), and stabbing with lines Agarwal
(Duke), Aronov (Polytech, NY) & Suri (St. Louis).
- Optimization problems are considered by Icking & Klein (FernU
Hagen) -- searching for the kernel of a polygon; by Agarwal (Duke) &
Sharir (Tel Aviv) -- randomized algorithms for width, etc; and by Dyer
(Leeds) -- parallel linear programming. Rege (UC Berkeley) considers a
practical algorithm for geometric theorem proving.
- GIS applications motivated four papers: cartograms,
Edelsbrunner & Waupotitsch (UIUC); map labeling, Wagner & Wolff (FU
Berlin); subdivision overlay, Finke & Hinrichs (WWU Muenster);
optimal segment intersection, Balaban (Russian Acad Sci).
- Graphics has another four: approximating form factors,
Pellegrini (Kings), polyhedral surface decomposition, Chazelle,
Dobkin, Shouraboura & Tal (Princeton); graph drawing, Di Battista
(Basilicata), Garg, Tamassia (Brown), Liotta, Tassinari & Vargiu (U di
Roma); reflections, Aronov (Polytech, NY), Davis (St. John's), Dey,
Pal & Prasad (IIT Kharagpur)
- Robotics applications include fixturing by Overmars, Rao, Schwarzkopf
& Wentink (Utrecht); collision detection for a rotating polyhedron by
Schoemer (Saarlandes) & Thiel (MPI Inf); and representation of
visibility graphs by Pocchiola (Ecole Norm. Sup.) & Vegter
(Groningen).
Special issues of Discrete and Computational Geometry and of
Computational Geometry: Theory and Applications will be dedicated to
the theoretical and the experimental and applied papers from the
conference. Proceedings are available from ACM Publications.
VIDEOS
David Dobkin (Princeton) chaired the 4th annual Video Review, taking
over from John Hershberger and Marc Brown. The six videos selected
(from nine submissions) show educational animations (Visibility
Complex, Pythagorean Theorem), new algorithms (Collision detection,
Convex Decomposition), and applications (Mechanism analysis, 3D
modeling). They were shown throughout the conference and distributed
to all registrants. Extra video tapes in NTSC, PAL, and SECAM formats
will be available from ACM Publications.
COMMUNICATIONS
The two-page communications were designed to inform the SCG community
of CG software and of applications of CG techniques that would
otherwise be published in diverse applications conferences or
technical report series. All but two of the 18 communications were
represented at the conference by a poster or demonstration. They
covered areas of Representation/Modelling, Visualization, Exact
Computation, Robotics, GIS, VLSI Layout, and other applications.
Thanks are due to Michael McAllister and Gwen Litchfield (UBC) for
configuring all the demos to work at UBC.
Unlike my experiences at other conferences, people actually talked to
the poster and demo presenters. In fact, everyone I asked thought
that the posters/demos were a good idea and several people said that
they would be submitting communications for the 1996 conference.
NEXT YEAR
The 12th ACM Symposium on Computational Geometry May 24--26, 1996,
will a part of the Federated Computing Research Conference in
Philadelphia. Program chair is Leonidas Guibas, Computer Science,
Stanford, CA 94305 USA. Papers and communications are due November 7,
which is a month earlier than usual. Videos are due to Marshall Bern
at Xerox PARC on January 6. Nina Amenta is the video chair. In 1997
the ACM SCG will be hosted by INRIA Sophia Antipolis, near Nice,
France.
Jack Snoeyink
Dept. Computer Science
University of British Columbia
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