Double Number of 2D Curves of Brep. Why?

Rhino Developer
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1

Hi there!
Im using rhinocommon (inside Grasshopper’s c# component) to get the 2D Curves of Breps (var crvs2d = brep.Curves2D).

In some cases, the number of 2D Curves is double the number of 3D Curves and the number of 2D Curves shown. It looks like all curves are returned twice.
Does anyone know why this is the case? Is it Nurbs-related thing?

Thanks for help!

2

The 2D curves are defined in face UV space, so whenever you have an edge in a brep where two faces meet, you have a single 3D curve (the edge you see) and two 2D curves.

3

Thanks for the quick reply!
You are right, but in my case the brep has only one face (meaning there arent any interior edges). In the meantime I also figured out, that this problem occurs for triangular (nurbs-)surfaces when they are modelled via command “_SrfPt” and only 3 points are defined.
I somehow solved the thing, by just deleting the doubled 2D curves in case the number of 3d and 2d curves do not match for a one-face brep, but I would like to understand if this has some Rhino Bug origin or is somehow related to nurbs…

4

Hi Philipp,
Shot in the dark:
Could it be they can be culled with:

http://4.rhino3d.com/5/rhinocommon/?topic=html/M_Rhino_Geometry_Brep_CullUnused2dCurves.htm

-Willem

5

seems to work perfectly fine!
Thanks willem!

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