SISL Homepage

Welcome to the home page of the NURBS (Non Uniform Rational B-Splines) software library SISL, developed and maintained by the geometry modelling group at SINTEF ICT, Department of Applied Mathematics.

The History of SISL


The story of SISL begins in the 1980s when we developed the NURBS library APS-SS in Fortran. Its design was based on requirements from industrial customers, who had considerable demands of the software. Based on this experience, in 1988 a NURBS library was developed in C, and dubbed SISL, the SIntef Spline Library. The new library contained numerous enhancements over the original Fortran version.

Since then SISL has been, and continues to be, used heavily by customers in Europe and the USA, and its functionality, stability and efficiency has been refined through consecutive releases, currently at number 4.2.

Key Functionality


SISL contains all the necessary functionality for building applications needing free form geometry, including:

  • Curve/surface creation.
  • Curve/surface interrogation.
  • Curve/surface manipulation.
  • Curve/surface intersections for both NURBS and analytical geometry.
  • Data reduction.

The high quality of the functionality and the high degree of accuracy in numerical calculations, has been developed to satisfy the exacting requirements arising when NURBS curves and surfaces are used in a CAD/CAM system.


Publisert 5. august 2014