Is there a VB equivalent to Sort Points Along Curve with point index map?

Replies to This Discussion

Permalink Reply by Thomas on October 19, 2013 at 9:35am

Hi Fernando,

something like that?

(first number = unsorted index, second number = sorted index)

I use Linq:

Dim getT = Function(pt As Point3d)
        Dim t As Double
        curve.ClosestPoint(pt, t)
        Return t
    End Function

Dim map = points.Select(Function(pt, i) New With {.T = getT(pt), .Index = i}) _
    .OrderBy(Function(p) p.T) _
    .Select(Function(p, i) New With {.T = p.T, .OldIndex = p.Index, .NewIndex = i}) _
    .OrderBy(Function(p) p.OldIndex) _
    .Select(Function(p) p.NewIndex) _
    .ToList()

Attachments:

• Map.3dm, 16 KB
• Map.gh, 9 KB

Permalink Reply by Fernando Conti on October 20, 2013 at 4:18am

Hi TJO,

Thank you so much, that is perfect!

I've never worked with Linq, but I have experience with writing sql queries, it's pretty much the same. It opens up so much possibilities for me, Grasshopper keeps getting better and better!

Just to be clear, you wrote:

map = points.Select(Function(pt, i) New With {.T = GetT(pt, curve), .Index = i}) _
.OrderBy(Function(pair) pair.T) _
.Select(Function(pair, i) New With {.OldIndex = pair.Index, .NewIndex = i}) _
.OrderBy(Function(p) p.OldIndex) _
.Select(Function(p) p.NewIndex).ToList()

instead of:

map = points.Select(Function(pt, i) New With {.T = GetT(pt, curve), .Index = i}) _
.OrderBy(Function(pair) pair.T) _
.Select(Function(p) p.Index).ToList()

because that extra part takes duplicate points into account, and makes sure that the original order is kept, right?

Thank you very much!

Permalink Reply by Thomas on October 23, 2013 at 12:44pm

I'm glad I could help!

You are right! The additional lines are restoring the original order of the points. Duplicate points should not make problems anyway. They keep their relative position.

Permalink Reply by Andy VanMater on October 22, 2013 at 3:16pm

I know that TJO solved your problem in a really cool 1 line code... but it kind of flew over my head so I just wanted to add my 2 cents and show the same solution without functions and on multiple lines

 


Private Sub RunScript(ByVal points As List(Of Point3d), ByVal curve As Curve, ByRef map As Object)
Dim nA(points.Count-1) As int32
Dim tA(points.Count-1) As int32

For i As int32 = 0 To points.Count - 1
Dim t As New Double
curve.ClosestPoint(points(i), t)
nA(i) = i
tA(i) = t
Next
Array.Sort(tA, nA)

map = nA

 

Permalink Reply by Thomas on October 23, 2013 at 1:24pm

Hi Andy!
Of course you can use Array.Sort(). Don't forget to sort the points back:

Dim n = points.Count()

Dim unorderedIndices(n - 1) As Integer
Dim orderedIndices(n - 1) As Integer
Dim t(n - 1) As Double

For i As Integer = 0 To n - 1
  curve.ClosestPoint(points(i), t(i))
  unorderedIndices(i) = i
  orderedIndices(i) = i
Next

Array.Sort(t, unorderedIndices)
Array.Sort(unorderedIndices, orderedIndices)

To get the ordered position of point i you can call: orderedIndices(i)
and you can get the parameter of point i by calling t(orderedIndices(i))

Permalink Reply by Fernando Conti on October 24, 2013 at 9:45am

Thanks Andy and TJO!