Mesh Srf from half/quater circle - Bug ref. vs. gh curves?

[danielbent (Daniel)]

Hey everyone,

I want to create a mesh of a half circle to play around with in kangaroo like this.

My first way was to draw the geometry in rhino, split the half circle in two quaters and loft each one with the vetrical split line to create surfaces that can be easily meshed with the Mesh Surface component.
Since Rhino 6 I get a invalid mesh out of the Mesh Srf comp but Combine&Clean does it’s job and I get a Mesh (V: 821 F: 800) that works fine in Kangaroo.

So I thought I could just create the curve geometry in gh to change the radius easily.
Again same way, but no invalid mesh out of the Mesh Srf comp and I get a Mesh (V: 841 F: 800). I tried it in Kangaroo and it didn’t work so I took a look at the mesh, and noticed that it has 20 interior edges with 0 length and 20 duplicate verticies (for the quaters the 0 length edges are exterior since they are located at the point where vertical line and arc intersect):

Since I don’t know how to rebuild the mesh without the 0 length edges/duplicate verticies I tried Mesh Loft and it works like intended.

But I wonder what is the difference between the referenced/internailized and the gh curves that allows this to happen?
I would love to understand what the problem is and how to solve it

Here my gh file:
half_circle_mesh_kangaroo_forum.gh (33.8 KB)

[Michael_Pryor (ekim)]

Because at the poles you get many overlapping verts which creates zero length edges and degenerate faces. Rhino 5 didn’t care about it but Rhino 6 flags it as invalid.

Mesh Surface (Mesh UV component) makes Invalid Mesh with Spheres (Rhino 6 + GH 1)

In Rhino 6 and GH 1 Mesh Surface component has issues with things like spheres because of the pole conditions. This isn’t an issue in R5. Only way I could get past it was to cull degenerate faces, then combine identical verts. This seems like a condition that shouldn’t create invalid meshes. [Capture] srfmsh.gh (7.2 KB)

[danielbent (Daniel)]

Hey Michael,
thanks for your answer. Yes i found this post of yours, but it doesn’t explain to me why the component notices the overplapping verts at the poles with rhino geometry but not with gh geometry.

Edit: I also did try to work with the C# script you provided in your post. It can fix the mesh build with rhino geometry but not the one build with gh geometry.

[HS_Kim]

As Michael Pryor said, if you would be able to delete 0 length mesh edges and rebuild it using Weaverbird’s Mesh From Lines, then, it should work fine.

half_circle_mesh_kangaroo_forum_re.gh (12.7 KB)