Disputation: Jostein Bratlie

Doctoral candidate Jostein Bratlie at the Department of informatics, Faculty of Mathematics and Natural Sciences, is defending the thesis Applications of blending splines in interactive geometric modeling for the degree of Philosophiae Doctor.

Picture of the candidate

Photo: Private

The University of Oslo is closed. The PhD defence and trial lecture will therefore be fully digital and streamed directly using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants -> Raise hand'. 

Trial lecture

" Methods for interpolation of scattered 3D data by smooth surfaces"

Main research findings

Blending spline constructions are generated by blending local geometry using a smooth basis function.
Compared with de facto industry standards used within CAGD, blending spline constructions are structurally complex.
However, they enjoy a combined set of unique properties that are exploitable in real-world applications.

This ph.d. thesis investigates some of the construction's curve and surface applications in interactive geometric modeling (IGM).
In particular, in the thesis's main contribution, the basis's property of vanishing derivatives is exploited to enable a patchwork interpretation for surface constructions.
Together with a salient API feature of modern graphics hardware, this enables cost-consistent evaluation schemes.
Moreover, the patchwork interpretation itself enables polygonal surface constructions with constant parameter lines that are non-dependent on the local surface type.

Software prototypes are utilized to develop and verify the thesis results.
An in-house library built on a set of salient features of modern C++ is used for this purpose.
With the thesis, a minimal feature version of this library is provided, and the feature utilization is argued.

Adjudication committee:

  • Associate Professor Krassimira Vlachkova, Sofia University, Bulgaria
  • Research manager Jon Mikkelsen Hjelmervik, Sintef, Norway
  • Professor Xing Cai, Department of Informatics, University of Oslo, Norway


  • Professor Arne Lakså, Department of Computer Science and Computational Engineering, UiT The Arctic University of Norway, Norway
  • Professor Knut Mørken, Department of Mathematics, University of Oslo  Norway

Chair of defence

  • Associate Professor Petter Nielsen, Department of Informatics, UiO

Contact information to Department: Mozhdeh Sheibani Harat

Publisert 27. mai 2021 16:35 - Sist endret 29. juni 2021 09:55