Line connection

Hi everyone,

I m learning grasshopper by my own and trying to understand a few things about the list

I am actually doing this tutorial (link below)

My first question concern the connection of a line (see the tutorial at 5:35min)
I don t understand why i don t get the same result when i connect my line to the two different explode component.

I think i should have the same result as the second option for both. please see the shotsreen attached

My second question concern the extrusion of my polygon (see the tutorial at 6:50min)

I don t understand why i need to join the curves to able an extrusion in the two senses.

Thank you by advance for your help


Check your connections. It looks like you connected the endpoint of the line component to the wrong component (it passes very close to the correct place)

I am not sure I understand your second question.

Your 1st question has to do with the Explode component automatically grafting each input:

  • 1st Explode takes in a curve and returns a single list of N curve segments,
  • 2nd Explode takes in those N curves and returns a Datatree structure with N branches and only one item per branch (since the segments can’t be divided further)

This means the downstream components will match things up differently - basically inputs are matched branch-by-branch and only broadcasted across lists:

I’m afraid I don’t understand your second question either.

Thank you very much for your answer but am really sorry it doesn t really help me

What i try to understand is how the list work.

In your first exemple I guess the vertex number 0 of the first list connects to the vertex number 0 of the second list. and the 1 to the 1 etc…

In your second example i don t understand how it works…

Then when i bake the lines I obtain infact 7 lines but not the lines i was expected.

see below what i expected : (sorry for my basics drawings in red)

What it happens is different and i don t understand the logic.
They don t reach all the points in a logic order and i find sometimes some lines which overlay and has the same length.

What i tried to understand in the previous tutorial is how the list work to connect the point and in which order.

Thank you for your time


What happens is that each of the (N=1) branches from the grafted component B is being matched up with the (N=7) branch from component A. So there are 7 lines being drawn per branch, each connecting the same vertex of B with all 7 vertices of A. This happens 7 times for each branch of B, for total of 49 lines.

I realise using a closed polygon as an example might have been confusing, because the start and end point is repeated. That’s why you get N=7 for a hexagon, the center point isn’t involved at all.

It is a tricky thing to get used to for most beginners, you can play around with the following: (9.7 KB)