Unitize a vector

I have the following code in a grasshopper VB.Net Script component:

Private Sub RunScript(ByVal S_Vector As List(Of Vector3d), ByRef S_Mid As Object)
Dim S_MidVector As New List(Of Vector3d)
Dim i As Integer

For i = 0 To S_Vector.Count - 2

S_MidVector.Add((S_Vector.Item(i) / S_Vector.Item(i).length) + (S_Vector.Item(i +_
1) /S_Vector.Item(i + 1).length))

S_MidVector.Item(i) = S_MidVector.Item(i).Unitize()

S_Mid = S_MidVector

End Sub

I get an error saying that type 'Boolean' cannot be converted to Rhino.Geometry.Vector3d, which apparently means that Unitize() is returning a boolean, rather than the unitized vector. How can I get the unitized vector?

Replies to This Discussion

Permalink Reply by raf2205 on January 23, 2012 at 3:36pm

just do

S_MidVector.Item(i).Unitize()

instead of

S_MidVector.Item(i) = S_MidVector.Item(i).Unitize()

;)

Permalink Reply by Larry Boxler on January 23, 2012 at 4:21pm

I did try that, but the vectors don't come out Unitized. The component output still has the initial length vectors.

Permalink Reply by David Rutten on January 24, 2012 at 1:54am

Vectors are value types, when you call:

S_MidVector.Item(i), you get a copy of the vector that's inside the list. Unitizing this copy won't affect the original vector. What you need to do:

Dim vec As Vector3d = S_MidVector.Item(i)

vec.Unitize()

S_MidVector.Item(i) = vec

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Larry Boxler on January 24, 2012 at 8:30am

Thank you for explaining that the .Item() call returns a copy. Explains why the .length property call worked in the previous line for what I was using it for and the .Unitize() method didn't work, which was why I was so confused.

Permalink Reply by David Rutten on January 24, 2012 at 8:41am

Ideally value types should not have methods that change the type variables. Ideally Unitize() should return a unitized vector rather than changing the xyz values of the vector itself. However we decided to not adhere to this guideline for RhinoCommon.

Native framework classes like Rectangle and PointF are also mutable, so even Microsoft breaks this rule.

David Rutten

david@mcneel.com

Poprad, Slovakia

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