AcRxObject AcGiDrawable AcHeapOperators AcDbObject AcDbEntity AcDbCurve AcDbSpline AcDbHelix
class AcDbHelix : public AcDbSpline;
dbhelix.h
This class implements the AutoCAD helix entity. AcDbHelix derives from AcDbSpline, but overrides the spline properties with its own behavior. Objects of the AcDbHelix class contain an embedded AcDbSpline which is wrapped by the AcDbHelix in order to constrain its behavior so that its basic shape is maintained. The behavior of calling NURB functions on the AcDbHelix class is unknown and not recommended.
When setting the constraints on a helix object, the order in which the set functions are called is important. Refer to ConstrainType for a detailed explanation.