Example:
;; Add Spline
(defun c:test ( / *mspace* p pts spline)
(setq *mspace*
(vla-get-ModelSpace
(vla-get-ActiveDocument
(vlax-get-acad-object)
)
)
)
(setq p (getpoint "\nPick point: "))
(while (setq p (getpoint p "\nPick point: ")) (setq pts (cons p pts)))
(setq pts (append pts (list (car pts))))
(setq spline
(vlax-invoke *mspace* 'AddSpline (apply 'append pts)
'(0.0 0.0 0.0) '(0.0 0.0 0.0)
)
)
(setq fd (vlax-curve-getFirstDeriv spline 0))
(vlax-put spline 'StartTangent fd)
(vlax-put spline 'EndTangent fd)
(princ)
)