Warning: this symbol is deprecated: Rendering of this is not portable to OpenGLES, and this is not really a useful curve for most practical game uses. For portable and fast curves consider using X3D NURBS nodes (wrapped in a TCastleScene) instead.
3D curve defined by three 1D natural cubic splines, automatically closed if first and last points match. This is the most often suitable non-abstract implementation of TNaturalCubicSplineCurve_Abstract.