I am bad at Meshes, why is Rhino triangulating this?

Hi I created a mesh with grasshopper, simple triangles.

I noticed some triangles were unnecessarily divided.

If my basic math is correct, a triangle is always planar, so I should be able to have this triangle here with not subdivisions.

I tried command ‘mergeface’ which works, but partially, because when I run ‘triangulate’ the edge is back…

mesh.3dm (46.8 KB)

Is there a better way to merge mesh faces creating a simple planar triangle instead of having to manuall delete the triangle and recreate it with command ‘3DFace’?

Hello- that looks wrong, or at least unexpected to me - merging leaves a vertex in the middle.



From what I can gather so far, that is ‘the way it is’ in Rhino for now.


Here’s a screenshot of Rhino 8 BETA. Nothing happens at all. The faces that seem coplanar are in fact not coplanar and at least that one vertex which remains is 0.00114 units off the line between the two adjacent points.

The easiest way to get rid of the extra points is the command _CollapseMeshVertex and click the three vertices.

Possibly the curves or geometry used to define the original mesh has an extra control point at those locations.

Hi Martin - as far as I can tell so far, the same happens if the polys are all in plane - I can reproduce the same thing from scratch.

RH-77042 Merging mesh faces leaves vertices



At least one of the vertices isn’t in line.

But as you wrote it also happens if everything is nicely planar and in line.

Adding Ngons to a mesh plane also does not eliminate any vertices.

I’m doing some kind of a mesh cleanup in Grasshopper using Kangaroo. I’m extracting naked edges of near coplanar faces, cull duplicate points, join the edges and rebuild the polylines with just the significant points.

Thank you guys for looking into this.

Martin, it would really useful if you can share that def! I think it would be a good idea to have some control over the threshold parameter? Like at what instance it considers faces planar or not.

I cannot share the definition. It’s too experimental and far from user friendly.