From a series of line segments to a polyline

[xuanshenyu]

I’ve got a series of line segments, and then I want to extract the outer boundary from them and make a polygon.
As follow:

[wim (Wim Dekeyser)]

Hi -

@xuanshenyu

I’ve got a series of line segments, and then I want to extract the outer boundary from them

Select all and run CurveBoolean.
-wim

[xuanshenyu]

I’m sorry I left out some key information about my question. I use the GH python to creat a series of line segments, and then I want to creat a outer boundary polygon by line segments in GH.

[René_Corella]

@xuanshenyu

I want to creat a outer boundary polygon

Maybe look into a ‘concave’ hull?

Wish: Concave Hull

Concave hull is a very common problem. I use the VB script from here: https://www.grasshopper3d.com/forum/topics/connecting-points-in-sequence It would be nice to have it in GH2.

Alternatively, if you’re able to join all those segments in a single polyline, then you could clean up intersections (including self-intersections) and keep ‘exterior’ segments?

[HS_Kim]

You could use Boundary Surfaces as well…

[inno]

if the segments are just disjointed lines, and if you are happy to use plugins, then Heteroptera and Fennec have viable components (see these two replies to the very same recent topic)

Couple of vector and region questions

The Heteroptera plugin has a Geometric Region component if you don’t mind using a plugin. [image]

Couple of vector and region questions

ohh yes I thought you were actually generating Polar Points for a purpose, and just wanted to get their lenght=1 vector about the boundary region, if you’re happy to use plugins Fennec also has a Region component with a boolean where you can combine all the regions together: [image]

[PeterFotiadis (Pfotiad0)]

@René_Corella

Maybe look into a ‘concave’ hull?

Not the answer for the general case (see Inner Loops):

[xuanshenyu]

Thank you for your answers, learned a lot of methods. But the method, using Boundary Surfaces, KIM mentioned was the best solution for my problem.

[xuanshenyu]

Bad luck, I was using RH8_GH and there was a BUG in the script battery calling the existing battery in GH.
For example:
import ghpythonlib.components as ghcomp
NFP_polygon = ghcomp.BoundarySurfaces(curves)

[René_Corella]

@xuanshenyu

using Boundary Surfaces

I didn’t suggest this one thinking the segments intersecting would cause it to fail:

However I probably don’t even know how ‘boundary surface’ works haha

[Helvetosaur]

@René_Corella

I didn’t suggest this one thinking the segments intersecting would cause it to fail

Me also in another thread… so it does work on these types of situations? I tried it in my example with just three intersecting lines and it didn’t work… Maybe I did something wrong, will try again.