;; | ----------------------------------------------------------------------------
;; | MI_IsPointOnCurve
;; | ----------------------------------------------------------------------------
;; | Function : Determines if the two points are on a curved path along a curve
;; |            or not.
;; | Arguments: 'ename'       - Name of the curve object along which to check
;; |            'pt'          - First point on curve to check
;; |            'SamplingInt' - Sampling Interval
;; | e-mail   : rakesh.rao@4d-technologies.com
;; | Web      : www.4d-technologies.com
;; | ----------------------------------------------------------------------------


(defun MI_IsPointOnCurve ( ename pt SamplingInt / OnCurve oname param1 param2 d
 fd1 fd2 )

(setq
	OnCurve nil
	oname   (vlax-ename->vla-object ename)
	param1  (vlax-curve-getParamAtPoint oname pt)
)

(if param1
(progn
	(setq fd1 (vlax-curve-getFirstDeriv oname param1))
	(if fd1
	(progn
		(setq d (vlax-curve-getDistAtParam oname param1))
		(if d
		(progn
			(setq
				d      (+ d SamplingInt)
				param2 (vlax-curve-getParamAtDist oname d)
			)
			(if param2
			(progn
				(setq fd2 (vlax-curve-getFirstDeriv oname param2))
				(if fd2
				(progn
					(if (not (equal fd1 fd2))
						(setq OnCurve T)
					)
				))
			))
		))
	))
))
(vlax-release-object oname)
OnCurve
)