Trimming curves in VB script component


I have a tree of curves that I’m trying to trim the ends off leaving a percentage of the curve behind in a VB component in Grasshopper, but am having some trouble. The issue I am having is that none of the curves seem to be getting modified in any way. Attached is what I am attempting, what have I messed up?


  Private Sub RunScript(ByVal InputCurves As DataTree(Of Object), ByVal OpenArea As Integer, ByRef A As Object) 
Dim pOpen As Double = OpenArea / 100
Dim i As Int32 = 0

Dim outTree As New DataTree(Of Curve)()

While i < InputCurves.BranchCount
  Dim j As Int32 = 0
  While j < InputCurves.Branch(i).Count
    Dim workingCurve As Curve = InputCurves.Branch(i)(j)
    Dim newDLength As Double = workingCurve.Domain.Length * (1 - pOpen)
    Dim newParam As Double = (workingCurve.Domain.Length - newDLength) / 2
    Dim oldLength As Double = workingCurve.GetLength
    workingCurve.Trim(newParam, newParam + newDLength)
    print("Old length: " & oldLength & ", new: " & workingCurve.GetLength)
    Dim Path As New GH_Path(i)
    outTree.Add(workingCurve, Path)
    j += 1
  End While
  A = outTree
  i += 1
End While

(David Rutten) #2

The Trim() method doesn’t affect the curve you call it on, it returns a new curve, which is the trimmed version of the old curve.

(David Rutten) #3

I’d also recommend not using while loops for iterating over collections, that’s why For and For Each were invented, but that’s not in itself a bug.


Hmm, I thought I tried that, but I must still be doing something wrong. The following gives me the error: Object reference not set to an instance of an object.

Dim newCurve As Curve = workingCurve.Trim(newParam, newParam + newDLength)


(David Rutten) #5

Are you certain workingCurve is not a null reference?