Merge polyline after offset

Hi All,

I would like to merge polylines after offset with common boundaries. Kindly have a look at the attached picture where I need top curves to become bottom curves.


use region union component

How two separate curves work as region union? you can do that only if it overlap each other

It could be better you read the help or posting example files !! Because your screen capture are not great help.

Refer the image attached. As you can see nothing happened, I mean union result

sorry my bad. I mean I need the centre line like in second image as attached in post which did not have it after union

Are you joking ?
Are you a completely beginner ?
You provide no file just a screen copy and you want others than you solve your problem. Rhinoceros and Grasshopper don’t “think” there are not AI !!
Merge union is working in you case it gives that

Guess how I did that ?

And what is not working in last question ?


Thank you very much for the screenshot. I am sure I am not a beginner. I think I have a bug in my gh. Check my attached files (4.3 KB)

Yes you are a beginner, in Rhinoceros, Grasshopper and also real live 2 objects are said to be close if a distance between them is less than a certain tolerance. So if you want to join 2 disjoined object you can play with tolerances. If it is not enough you will have to use special script to deal with this problem. Like the ones that are here

I managed to solve this using bowerbird offset component, which is neat.

Now I am trying to expand my closed polyline region to empty space by replacing closed polyline with much bigger polyline occupying empty space nearby. Kind of like voronoi where after circle clashing it offset on other side and on clash side it remains straight. Although still not efficient for this.

I thought Offset Polyline was “But it is far from what I like to achieve” !!
Clipper and Bowerbird uses the same algorithm

The clipper component creates boundary of two regions right? like bower bird offset. But I need its intersecting line too. When two polyline offset and when offset lines touch each other it should not cross each other rather stays. If offset is increased further only other sides increase.

Using Clipper


curve (6.7 KB)

Ethan, I already gave this solution here but Mister The Great Saiya Man was not happy with that

OK Laurent, I’ll stay out of it.

Yes but I couldnt install clipper in my rhino 5. Says its incompatible. Is there any other way to get the code? please help

It is a bit strange you can’t install it, there is 2 versions in Fodd4Rhino. I use Clipper for years in Rh5 and 6. But if it work the same with Bowerbird, you can stay with bowerbird. The trick is to offset in one direction and then in the other.

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Bowerbird does the same exact thing too. But I need a centreline on those gap after merging.

is it possible to get the line at point of contact like this?