Segment.GetTangentAt

Function GetTangentAt([Offset As Double = 0.5], [OffsetType As cdrSegmentOffsetType = cdrParamSegmentOffset]) As Double

Member of Segment

The GetTangentAt method returns the angle of the tangent at a specified point on a curve segment.


Parameters	Description
Offset	Specifies the offset, in document units, from the beginning of a segment’s subpath This parameter is optional, and its default value is 0.5.
OffsetType	Specifies the type of offset of a point on a curve’s subpath. This parameter returns cdrSegmentOffsetType. This parameter is optional, and its default value is cdrParamSegmentOffset (2).

The following code example draws perpendicular and tangent vectors for several points uniformly distributed along the segments of the selected curve:

Sub Test() 
 Dim seg As Segment 
 Dim t As Double 
 For Each seg In ActiveShape.Curve.Segments 
  For t = 0 To 10 Step 2 
   MarkPoint seg, t / 10 
  Next t 
 Next seg 
End Sub 
Private Sub MarkPoint(seg As Segment, t As Double) 
 Dim x As Double, y As Double 
 Dim dx As Double, dy As Double 
 Dim a1 As Double, a2 As Double 
 seg.GetPointPositionAt t, cdrRelativeSegmentOffset, x, y 
 a1 = seg.GetTangentAt(t, cdrRelativeSegmentOffset) * 3.1415926 / 
180 
 a2 = seg.GetPerpendicularAt(t, cdrRelativeSegmentOffset) * 
3.1415926 / 180 
 dx = 0.5 * Cos(a1) 
 dy = 0.5 * Sin(a1) 
 With ActiveLayer.CreateLineSegment(x, y, x + dx, y + dy) 
  .Outline.EndArrow = ArrowHeads(1) 
 End With 
 dx = 0.5 * Cos(a2) 
 dy = 0.5 * Sin(a2) 
 With ActiveLayer.CreateLineSegment(x, y, x + dx, y + dy) 
  .Outline.EndArrow = ArrowHeads(1) 
 End With 
End Sub