How to determine if a straight line is parallel to the x or y axis in the plane, and there is also a method of approaching parallelism

What’s the purpose of the check?

It looks like you’ve got line segments in the picture, not lines.

You might consider the following approach:

Take the normal of the plane and compare it to the line segment vector

It’s a straight line. I can’t find a way in Python. Can you help me write a copy

It is to determine whether the straight line is parallel or inclined to be parallel to the x and y axes of the plane

Can you show us the inputs to the function you have?

Are they a Rhino.Geometry.Plane and a Rhino.Geometry.Line?

Try to translate this C# to P:

PS: Or use **utol** instead (as an user defined value). Say:

utol = (utol < atol)? atol : utol;

BTW: This is an entry level C# that does that:

Line_ParToPlaneXY_V1.gh (117.9 KB)

BTW: For testing if a Line is par to a Plane (in general) get **pt1** as line.From clostest to plane and **pt2** as line.To closest to plane and test Math.Abs(line.Direction.IsParallel(pt2-pt1, tol)) - provited that:

- either pt2.DistanceTo(pt1) > tol [else Line is perp to Plane]
- or Math.Abs(line.Direction.IsParallel(Plane.ZAxis, tol)) != 1 [else Line is perp to Plane] .

The RhinoCommon line, vector and plane structs provides all you’d need For instance, you could go:

`myLine.Direction.IsParallelTo(myPlane.XAxis)`

See this documentation.

https://developer.rhino3d.com/api/rhinocommon/rhino.geometry.line/direction

https://developer.rhino3d.com/api/rhinocommon/rhino.geometry.vector3d/isparallelto

https://developer.rhino3d.com/api/rhinocommon/rhino.geometry.plane/xaxis

Thank you for resolving it

yes， I am currently facing a problem where the parallelism and verticality of lines are different when the plane is different. I don’t know how to use Python to solve this problem

Two posters just gave you the exact reference to the functions you need to call.

How far did you get?

Creating a Python script?

Finding the line and plane with the script?

Checking whether they’re parallel?

Thank you, it has just been resolved

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