Øyvind Hjelle
(... the page is not properly updated ...)Postal Address: 
Simula Research Laboratory P.O. Box 134 N1325 Lysaker, Norway Coordinates 
... 
Telephone:  Office and mobile: +47 93 45 48 31, Fax: +47 67 82 82 01  
Email:  oyvindhj 'paa' simula.no 
Positions:
Chief Scientific Programmer, Kalkulo AS
(subsidiary of Simula Research Laboratory), present
Associate
Professor (Førsteamanuensis II), University of Oslo,
Department of Informatics, 2000  2010
Former: Senior research
scientist/Research Manager, SINTEF Applied
Mathematics
Research activities and teaching:
Mathematical modeling of folding and deformation in structural geology
Level Set methods
Multigrid techniques in scattered data modelling
Generic programming: TTL, The Triangulation Template Library
Teaching: INFMAT5370, Triangulations and Applications
Teaching: INF2340, Simulation and Visualization
Other research areas and interests:
Multiresolution modelling of huge data sets  Scattered data modelling 
Medical imaging  Visualisation 
Computational neuroanatomi and neuroinformatics  Geological modelling and seismics 
Triangulations and Meshing  Bspline curves and surfaces 
Multigrid techniques  Surface reconstruction 
Generic programming  CAD/CAM/GIS/ GIT 
Participating in Oslo Graphics Lab (OGL).
Teaching at The University of Oslo.
Since 1999 I have developed and taught the course INFTT at the University of Oslo together with
Morten Dæhlen,
Department of Informatics (IFI).
From 2003 the course is part of IFI's
master programs and taught under
INFMAT5370, Triangulations and Applications.
Slides and information relevant for classes can be found here.
In 2004 I am teaching INF2340, Simulation and Visualization together with Trygve K. Nilssen (Simula Research Lab).
LSBINTR: Multilevel least squares approximation of scattered data over binary triangulations
This is a powerful method for approximating huge scattered data sets.
The approximation scheme generates multilevel triangulations obtained using
a subdivision scheme known as longest edge bisection. Nested function spaces
are defined over the multilevel triangulations. The approximation problem is
solved by successive refinement of the triangulation while iterative methods
are used for solving a system of linear equations at intermediate levels of
the multilevel scheme. Regularization terms are coupled with a standard
least squares formulation to guarantee uniqueness and control smoothness of
the solution.
See publication
in "Computing and Visualization in Science" and more details in the book:
Øyvind Hjelle and Morten Dæhlen. Triangulations and Applications.
SpringerVerlag, 2006.
Some software libraries implemented in research activities at SINTEF Applied Mathematics:
MBA: Multilevel Bspline Approximation of Scattered Data
LSMG: A Multigrid Approach to Scattered Data Modelling with Bsplines
A multigrid approach for reconstruction of surfaces from scattered
data. I developed this library in a FrenchNorwegian project
supported by the
FrenchNorwegian Foundation.
Ecole des Mines de Paris and The
French Petroleum Institute (IFP) participated on the French
side, and Geocap a.s.
participated on the Norwegian side. These companies all use LSMG,
together with MBA above and TTL below, in their geological modelling
applications for modelling geological faults and horizons from
interpreted seismic data. The 3D model shows Utladalen in
Jotunheimen, Norway, in the centre of the picture. Store
Skagastølstind is in the mountain range to the left; Skogadalsbøen
in the far end of Utladalen, and Hjelledalen is the valley on the
right. A GPL version of the software is available here.
TTL: The Triangulation Template Library
A generic library for Delaunay triangulation. The animation
demonstrates some features of TTL: Insertion and deletion of nodes, and
insertion of constrained edges. The triangulation is always maintained as a CDT
(Constrained Delaunay Triangulaton.).
Follow the link and learn more about TTL, especially about its generic
programming philosophy which enables TTL's algorithms to work on arbitrary
data structures for triangulations.
The generic programming philosophy of TTL is published as one of the
chapters the book:
Øyvind Hjelle and Morten Dæhlen. Triangulations and Applications.
SpringerVerlag, 2006.
I have also been heavily involved in the development of these libraries:
Siscat, The SINTEF Scattered Data Library
SISL,
The SINTEF Spline Library
Some clients and collaborators through projects at SINTEF
Applied Mathematics and Simula Research Lab.:
Statoil ASA
The French Petroleum Institute (IFP)
Ecole des Mines de Paris
Kongsberg
Defense & Aerospace
The Interventional Centre
at Rikshospitalet University Hospital in Oslo
NeSys, Neural Systems and Graphics
Computing Laboratory at the University of Oslo
GeoCap
Some publications, not properly updated (see also under www.simula.no):
Books and lecture notes:
Ø. Hjelle and M. Dæhlen.
Triangulations and Applications, SpringerVerlag, 2006 (234 pages, 126 illustrations, ISBN: 9783540332602).
Available, e.g., at
Amazon
or
Springer.
Used in the course
INFMAT5370
at the University of Oslo, Department of Informatics.


Ø. Hjelle. PhD thesis from Delft University of Technology: A HamiltonJacobi Framework for Modeling Geological
Folding and Deformation. (Can be downloaded from the digital library at TU Delft) 
Some other other publications and preprints (not properly updated, see under www.simula.no):
Some SINTEF reports:
Other publications:
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