Specifies the start tangent for the spline.
Supported platforms: Windows only
Read-only: No
Type: Variant (three-element array of doubles)
A directional vector representing the start tangent of the spline.
When a spline is elevated, it is converted from an interpolated (fit) spline to a control point spline. This means that after elevation, the spline no longer has fit tangents, and the StartTangent and EndTangent properties for the spline are no longer accessible. The only way to edit a control point spline is through the ControlPoints property, or the SetControlPoint or GetControlPoint methods.
VBA:
Sub Example_StartTangent() ' This example creates a spline. It then queries the current setting for ' the StartTangent, and then changes the StartTangent to a new value. ' Create the spline Dim splineObj As AcadSpline Dim startTan(0 To 2) As Double Dim endTan(0 To 2) As Double Dim fitPoints(0 To 8) As Double Dim msg As String startTan(0) = 0.5: startTan(1) = 0.5: startTan(2) = 0 endTan(0) = 0.5: endTan(1) = 0.5: endTan(2) = 0 fitPoints(0) = 1: fitPoints(1) = 1: fitPoints(2) = 0 fitPoints(3) = 5: fitPoints(4) = 5: fitPoints(5) = 0 fitPoints(6) = 10: fitPoints(7) = 0: fitPoints(8) = 0 Set splineObj = ThisDrawing.ModelSpace.AddSpline(fitPoints, startTan, endTan) ThisDrawing.Regen True GoSub GETPOINTS MsgBox "The StartTangent for the spline is " & msg, vbInformation, "StartTangent Example" Dim newTan(0 To 2) As Double newTan(0) = 1.5: newTan(1) = 0.707: newTan(2) = 2 ' Change the start tangent of Spline to (1.5, 0.707, 2) splineObj.EndTangent = newTan ThisDrawing.Regen True GoSub GETPOINTS MsgBox "The StartTangent has been changed to " & msg, vbInformation, "StartTangent Example" Exit Sub GETPOINTS: Dim count As Integer msg = "" ' Get the coordinates from the start tangent For count = 0 To 2 msg = msg & Format(splineObj.StartTangent(count), "0.###") & ", " Next msg = VBA.Left(msg, Len(msg) - 2) Return End Sub
Visual LISP:
(vl-load-com) (defun c:Example_StartTangent() ;; This example creates a spline. It then queries the current setting for ;; the StartTangent, and then changes the StartTangent to a new value. (setq acadObj (vlax-get-acad-object)) (setq doc (vla-get-ActiveDocument acadObj)) ;; Create the spline (setq startTan (vlax-3d-point 0.5 0.5 0) endTan (vlax-3d-point 0.5 0.5 0) fitPoints (vlax-make-safearray vlax-vbDouble '(0 . 8))) (vlax-safearray-fill fitPoints '(1 1 0 5 5 0 10 0 0 ) ) ;; Create the spline (setq modelSpace (vla-get-ModelSpace doc)) (setq splineObj (vla-AddSpline modelSpace fitPoints startTan endTan)) (vla-ZoomAll acadObj) (setq msg "") ;; Get the coordinates from the start tangent (setq startTangent (vlax-safearray->list (vlax-variant-value (vla-get-StartTangent splineObj)))) (setq msg (strcat msg (rtos (nth 0 startTangent) 2 3) "," (rtos (nth 1 startTangent) 2 3) "," (rtos (nth 2 startTangent) 2 3))) (alert (strcat "The StartTangent for the spline is " msg)) ;; Change the start tangent of Spline to (1.5,0.707,2) (setq newTan (vlax-3d-point 1.5 0.707 2)) (vla-put-StartTangent splineObj newTan) (vla-Regen doc :vlax-true) (setq msg "") (setq startTangent (vlax-safearray->list (vlax-variant-value (vla-get-StartTangent splineObj)))) (setq msg (strcat msg (rtos (nth 0 startTangent) 2 3) "," (rtos (nth 1 startTangent) 2 3) "," (rtos (nth 2 startTangent) 2 3))) (alert (strcat "The StartTangent has been changed to " msg)) )