Projecting a cylinder to a plane - Wrong number of edges

Hi All,
I am having issues using the project component to push a cylinder into a 2D Plane.

The surface seems to be working OK, except that it is defined by only 3 Lines, where I should get a rectangular surface defined by 4 lines?

This is part of a bigger project where I am presenting geotechnical information from a 3D field onto a 2D plane, so i created a simple script to demonstrate the issue:

Cylinder (5.6 KB)
Cylinder Projection.3dm (72.5 KB)

If anyone can give me advice on how to project this so that I get a surface with four edges, that would be great!


I have not yet found a ‘solution’ but did find a workaround…

By projecting the cylinder, and feeding the plane of the projection into a bounding box I can take the bounding box edges which gives me a normally defined surface… I presume the projection issue is something to do with the way the cylinder is defined…

Its not a very pretty solution… but it works (for now)

You can use make2d if you use Rhino 6.

You are projecting a brep containing three faces and three loops (two circular edges and a seam edge) onto a plane where it ends up looking like a rectangle. This will not result in valid geometry, as two faces and two loops are squished flat, and the remaining face is folded in on itself. Or even if the result is strictly speaking valid, you’ll run into all sorts of problems trying to use such a shape in subsequent operations.

As mentioned, the Make2D approach was designed for this, but there are cheaper ways in Rhino as well to get silhouette curves. There’s also a Mesh Shadow component which may do what you want: (5.9 KB)

Thank you gents,
We have Rhino 6, but i am still using Rhino 5, simply because some of the components in the FabTools plugin are incompatible with 6.

I will try the mesh shadow component - see how it goes!