Feeding grasshopper script back into itself?

Replies to This Discussion

Permalink Reply by Evert Amador on October 25, 2010 at 3:15pm

Hi Zygnoth,

Is the distance between points along the curve the same?, if so the DivideByDistance component should fo the trick!

Cheers!

Evert

Permalink Reply by Zygnoth Cosmos on October 25, 2010 at 4:55pm

Thanks Evert, that does the trick alright!

But as a technique, is there another way of doing it - where you feed one end of a script back into the first part again? By using the same operator but feeding its own output back into its input?

I realise that this could lead to scripts diverging but can it work as a process for grasshopper or is this offbounds?

Attachments:

• quick grab.PNG, 101 KB

Permalink Reply by taz on October 25, 2010 at 4:49pm

Evert is right.

And also if your curves are non-planar the routine would be distances based on sphere/curve intersection points.

Hence the [Divide Distance] icon...

Permalink Reply by Zygnoth Cosmos on October 25, 2010 at 4:57pm

Thanks Taz,

I guess the question wasn't so much about the correct routine to use (which I obviously didn't know about but great to know now!) but about whether grasshopper can feed into itself...

Permalink Reply by taz on October 25, 2010 at 5:40pm

Recursion can only be done with a scripted component. So you would have to use VB.NET/C# and pick up some RhinoCommon.

Andrew Heumann was playing around with recursive-like operations so you could check this out:

http://heumanndesigntech.wordpress.com/2010/08/13/iteration-in-gras...

Permalink Reply by Evert Amador on October 26, 2010 at 3:40am

Hi taz,

Thanks for the link looks very interesting, I'll check it out. I've been doing some research on closed form sequences to try to generate recursion based on simple functions and no scripts. I'll post something when I get results.

Cheers

Evert

Permalink Reply by Shawn Fernandez on October 27, 2010 at 11:03am

This is part of the reason why we have boon looking forward to clusters for some time. With a centralized definition that can update all instances, clusters offer us a way to not only perform a limited level of recursion, but also to keep the canvas space organized and (relatively) easy to follow at the same time. Even with clusters though you are limited to knowing ahead of time how many times you will loop the function back on itself. You can currently only do true looping in script.

Permalink Reply by Zygnoth Cosmos on November 7, 2010 at 2:44am

Have you managed to create some looping in the scripting?

I've tried but I can't stop the VB script from taking all the inputs at the same time instead of constantly updating them. I'm probably not well read enough in VB to know if I'm doing this wrong...

Permalink Reply by Shawn Fernandez on November 8, 2010 at 7:22am

If you set the Input type on the component to list, you can then iterate through the list using a For loop. Something like this ...

RunScript(ByVal L1 As List(Of Object), ByVal A As String, ByRef L2 As Object)
Dim strTest As String
Dim listL2 As New List(Of Object)

For i As Integer = 0 to L1.Count - 1
If L1(i).To_String = strTest Then
listL2.Add(L1(i))
End If
Next i
L2 = listL2
End Sub



This component would iterate through each element in the input list and add it to the output only if it's ToString matches the input of A. This means no Null values for unmatched data branches.

Remember that all components have an inherent limited version of 'For Each' in that it will perform the function of the component upon each data branch passed to it. Most of the time you don't need to replace this For loop unless you want to selectively or corporately process the data.

Hope this helps!