Spline Curves

C3D Solver uses NURBS curves as a mathematical basis for spline curves. NURBS presentation has de-facto become an industry standard used to present free-form curves, and it is supported by almost all CAD systems. The NURBS Book by Les Piegl and Wayne Tiller (Springer Publishing Company) is a widely recognized canonical book in this subject domain.

C3D Solver offers two spline definition methods:

  • a spline constructed based on a set of characteristic points defined by their coordinate values;

  • a spline that passes through a set of interpolation points defined by descriptors of previously registered geometric objects.

A spline can be created from a NURBS curve based on

geom_item GCE_AddSpline(GCE_system gSys, GCE_spline spl).

The function accepts GCE_spline data structure that contains data defining the spline: the starting values of control points, the interpolation point array (if required), weights, closedness indicator, etc.

A special constraint that fixes the spline derivative vector is created by

constraint_item GCE_FixSplineDerivative(GCE_system gSys, geom_item spline
                                     , double par
                                     , uint derOrder
                                     , GCE_vec2d * fixVal = NULL )