Øyvind Hjelle

(... the page is not properly updated ...)

Postal Address:
Simula Research Laboratory
P.O. Box 134
N-1325 Lysaker, Norway

Coordinates

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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: INF-MAT5370, Triangulations and Applications
    Teaching: INF2340, Simulation and Visualization

Other research areas and interests:

Multi-resolution modelling of huge data sets Scattered data modelling
Medical imaging Visualisation
Computational neuroanatomi and neuroinformatics Geological modelling and seismics
Triangulations and Meshing B-spline 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 INF-TT 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 INF-MAT5370, 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).


Software Libraries

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 multi-level 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. Springer-Verlag, 2006.

 


Some software libraries implemented in research activities at SINTEF Applied Mathematics:

MBA: Multilevel B-spline Approximation of Scattered Data
A library developed for fast reconstruction of 3D models from scattered data. The method has multilresolutional properties which enables fast view dependent visualisation. It can also be used as a "preconditioner" for other algorithms for surface reconstruction (like LSMG below). The library is based on a scheme by S. Lee, G. Wolberg and S. Y. Shin from 1997. A GPL version of the software is available here.
 

 

LSMG: A Multigrid Approach to Scattered Data Modelling with B-splines
A multigrid approach for reconstruction of surfaces from scattered data. I developed this library in a French-Norwegian project supported by the French-Norwegian 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. Springer-Verlag, 2006.

 

 



I have also been heavily involved in the development of these libraries:

Siscat, The SINTEF Scattered Data Library
               
 

SISL, The SINTEF Spline Library
   

and to some extent,

Diffpack


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, Springer-Verlag, 2006 (234 pages, 126 illustrations, ISBN: 978-3-540-33260-2). Available, e.g., at Amazon or Springer. Used in the course INF-MAT5370 at the University of Oslo, Department of Informatics.
 
Ø. Hjelle. PhD thesis from Delft University of Technology: A Hamilton-Jacobi 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):

Ø. Hjelle and S. A. Petersen. A Hamilton-Jacobi Framework for Modeling Folds in Structural Geology. "Mathematical Geosciences", 43(7), 741 -- 761, 2011.
 
Ø. Hjelle, S. A. Petersen and A. M. Bruaset. A Numerical Framework for Modeling Folds in Structural Geology. "Mathematical Geosciences", 45(3), 255--276, 2013.
 
T. Gillberg, Ø. Hjelle and A.M. Bruaset. Accuracy and Efficiency of Stencils for the Eikonal Equation in Earth Modelling, Computational Geosciences, 16(4):933–952, 2012.
S.A. Petersen, Ø. Hjelle and others. EAGE-papers, refereed proceedings from 2007, 2008, 2012
(see under http://www.earthdoc.org)
T. Gillberg, Ø. Hjelle and A. M. Bruaset. EAGE-paper, refereed proceeding, 2012
(see under http://www.earthdoc.org)
T. Gillberg, Ø. Hjelle and A. M. Bruaset, and others. Journal papers and refereed proceedings up to 2014
(see publications at http://www.simula.no)
R. Lorentzen, Ø. Hjelle, H. P. Langtangen, and A. M. Bruaset, Extrapolation from a very Low Number of Computer Experiments, Simula Research Laboratory, 2010. (Preprint, Simula Technical Report Series)
Ø. Hjelle and M. Dæhlen. Multilevel least squares approximation of scattered data over binary triangulations. "Computing and Visualization in Science", 8(2), 83 -- 91, April 2005.
 
M. Dæhlen, M. Fimland and Ø. Hjelle, A Triangle-based carrier for geographical data.
Spatial Information and the Environment, Peter Halls (ed.), Taylor and Francis Books Ltd, 2001, 105-120. (Presented at GISRUK, York, April 2000.)
 
Y. Halbwachs and Ø. Hjelle, Generalized maps in geological modeling: Object-oriented design of topological kernels, In H. P. Langtangen and A. M. Bruaset and E. Quak, editors, Advances in Software Tools for Scientific Computing, pages 339 - 356, Springer, 1999.
 
M. Floater, Y. Halbwachs, Ø. Hjelle, and M. Reimers. OMEGA: a CAD-based approach to geological modelling. In proceedings from the GOCAD ENSG Conference, Nancy, June 4-5, 1998.
 
  E. Arge and Ø. Hjelle. Object-oriented scattered data modelling with Siscat. In E. Arge, A. M. Bruaset, and H. P. Langtangen, editors, Modern Software Tools for Scientific Computing, pages 289 - 308. Birkhäuser, 1997.
 
  N. P. Fremming, Ø. Hjelle, and C. Tarrou. Surface modelling from scattered geological data. In M. Dæhlen and A. Tveito, editors, Numerical Methods and Software Tools in Industrial Mathematics, pages 305 - 320. Birkhäuser, 1997.
 
  E. Arge and Ø. Hjelle. Software tools for modelling scattered data. In M. Dæhlen and A. Tveito, editors, Numerical Methods and Software Tools in Industrial Mathematics, pages 47 - 62. Birkhäuser, 1997.
 
  E. Arge, M. Dæhlen, and Ø. Hjelle. Mathematical software for terrain modeling. In J. T. Bjørke, editor, ScanGIS'95, The fifth Scandinavian Research Conference on Geogaphical Information Systems, pages 297 - 309. Trondheim, Norway, 1995.
 
  Ø. Hjelle and O. A. Steinlein. Compact digital representation of seismic sections. In proceedings from the 62nd Annual International SEG meeting, New Orleans, Oct. 25-28, 1992.
 
  Datareduksjon av høgdekurver. Ø. Hjelle and M. Dæhlen. Kart og Plan, Vol. 49, 469 - 471, 1989. Aas-NLH, ISSN 0047-3278.
 
Ø. Hjelle. A Triangulation Template Library (TTL): Generic Design of Triangulation Software. Technical Report STF42 A00015, SINTEF Applied Mathematics, Oslo, 2000. (Preprint.)
 
J. R. Sulebak and Øyvind Hjelle, Multiresolution Spline Models and their Applications in Geomorphology, Concepts and Modelling in Geomorphology: International Perspectives, Eds. I. S. Evans, R. Dikau, E. Tokunaga, H. Ohmori and M. Hirano, pp. 221--237. Tokyo, Japan, 2003.

Some SINTEF reports:

Ø. Hjelle, Approximation of scattered data with multilevel B-splines. Technical Report STF42 A01011, SINTEF Applied Mathematics, Oslo, 2001.
 
Ø. Hjelle, Explicit surfaces in Siscat. Technical Report STF42 A96008, SINTEF Applied Mathematics, Oslo, 1996.
 
Ø. Hjelle, Data structures in Siscat. Technical Report STF42 A96007, SINTEF Applied Mathematics, Oslo, 1996.
 
Ø. Hjelle, C++ Programming and functionality standard. Technical Report STF42 A96009, SINTEF Applied Mathematics, Oslo, 1996.
 
M. Dæhlen and Ø. Hjelle. Compact representation of seismic sections. Technical Report ISBN 82-411-0386-7, SINTEF Applied Mathematics, Oslo, 1992.
 
  M. Dæhlen and Ø. Hjelle. A Hierarchical Framework for Triangle-Based Surfaces and Polygonal Networks. Technical Report ISBN 82-14-01595-2, SINTEF Applied Mathematics, Oslo, 1999.
 

Other publications:

   

   

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