21WOJP – Week 18: Extracting Contours at Elevation

If you want to have all the power on how contours are created, you can always use the ‘ExtractContourAt()’ method. This method allows you to specified an elevation value at which the contours should be extracted, which in turn, gives you all the flexibility to extract contours using any kind of logic you will like. Of course, you want to insure the specified elevation is within the Surface’s elevation range.

The following command shows how the method is invoked to extract contours at a specified elevation, and how you can check the specified elevation is in range.

C#

[CommandMethod("CDS_ExtractSurfaceContoursAtElevation")]
public void CDS_ExtractSurfaceContoursAtElevation()
{
  using (Transaction tr = startTransaction())
  {
    ITerrainSurface surface = getSurface() as ITerrainSurface;
    if (surface == null) return;

    double elevation = getDouble("elevation");
    if (Double.IsNaN(elevation)) return;

    if (elevationInSurfaceRange(elevation, 
      surface as CivilSurface))
    {
      ObjectIdCollection contours = 
        surface.ExtractContoursAt(elevation);
      customizeContours(contours, _singleContourColor);
    }

    tr.Commit();
  }
}

private bool elevationInSurfaceRange(double elevation, 
  CivilSurface surface)
{
  GeneralSurfaceProperties properties = 
    surface.GetGeneralProperties();
  if (elevation < properties.MinimumElevation || 
    elevation > properties.MaximumElevation)
  {
    _editor.WriteMessage(
      "\nSpecified elevation not in surface range.");
    return false;
  }
  return true;

}

VB.NET

<CommandMethod("CDS_ExtractSurfaceContoursAtElevation")> _
Public Sub CDS_ExtractSurfaceContoursAtElevation()
  Using tr As Transaction = startTransaction()
    Dim surface As ITerrainSurface = TryCast(getSurface(), 
      ITerrainSurface)
    If surface Is Nothing Then
      Return
    End If

    Dim elevation As Double = getDouble("elevation")
    If [Double].IsNaN(elevation) Then
      Return
    End If

    If elevationInSurfaceRange(elevation,
        TryCast(surface, CivilSurface)) Then
      Dim contours As ObjectIdCollection =
        surface.ExtractContoursAt(elevation)
      customizeContours(contours, _singleContourColor)
    End If

    tr.Commit()
  End Using
End Sub

Private Function elevationInSurfaceRange(elevation As Double,
    surface As CivilSurface) As Boolean
  Dim properties As GeneralSurfaceProperties =
    surface.GetGeneralProperties()
  If elevation < properties.MinimumElevation Or
      elevation > properties.MaximumElevation Then
    _editor.WriteMessage(
      vbLf & "Specified elevation not in surface range.")
    Return False
  End If
  Return True

End Function

As always, you can download the full source code from the Civilized Development repository.