Cannot set any existing geometry - Rhino 6

For the last few days I have had a problem with my install of Rhino which makes it unusable.
I cannot set existing geometry as a line in grasshopper.

To recreate, I can restart Rhino, new file, draw a simple straight line.
Start GH, add a “line”, right click “set one line”.

Rhino will not let me select the existing line, it goes straight to: “start of line” and wants me to draw a new line. (see picture)
Even if I pre-select the line in Rhino before I right click “set one line” its still will not select it.

There must be some easy way to fix this, becuase without being able to assign geometry, I can’t get on with this project I’m really excited to work on. Can anyone help?

Windows 10.
Rhino Version: (6.29.20238.11501, 08/25/2020)
GH version: Build 1.0.0007 25 August 2020

Thank you in advance.

Why don’t you try use Geometry component instead of Line ? It should solve your problem because Geometry also can define Line object.


Hi Oğuzhan,
A good suggestion thank you, it get’s my definition to work, but it is a bit of a work around.
And it doesn’t really solve the bigger problem, that my line component is still not working correctly.
I cannot “set 1 line” or “set multiple lines”.
On the upside I now can set a pre-existing point, which I’m pretty sure that point was not working yesterday.

Hi Drew,

As I know, this is causing from implicit definitions of objects. For example, everything works with Vector objects but this object acts like abstract object for other definitions mathematically. This Line object simply works similar with Vector in Grasshopper, I mean as abstract object. Because of parameterizing possibilities of Grasshopper you can create this kind of abstract objects but they are not explicitly exist in Rhino. I believe that’s why you can’t select them directly by using “set one line”. Please warn me if I am wrong @DavidRutten

So, I would like to suggest to you simply use Curve component. Because you can use other components which are related to Line.


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Hi Oğuzhan,
I’ve looked into it, and you’re right. Thanks for your help, using Geo or curve solves it.
The line doesn’t behave the same as the Curve, Point or Geo components.
I’m not sure if it’s a feature or a bug.

Not a really a feature, but intentional nonetheless.

In Rhino, a line or circle curve can become another type of curve using any number of commands or control-point editing. However in grasshopper the Line and Circle parameters can only contain exact lines and circles. Thus, any referenced line may turn into a Nurbs curve at which point the referencing will fail.

This is why only the Curve parameter can reference objects, because once a curve, always a curve. The conversion from curve to line must then happen explicitly in grasshopper.

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