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.


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

The following VBA 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 x, y, t, cdrRelativeSegmentOffset

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