Ngon ivy

Is there some way to utilize Ivy to unfold a collection of Ngons? I am trying to unfold the dual of a triangular mesh--basically a bunch of 5-, 6-, and 7-sided polygons.

Is it possible to use Ivy with a list of polylines? Or is there someway to rebuild the mesh dual after unfolding the original triangular mesh, rather than building it before unfolding?

Replies to This Discussion

Permalink Reply by Andrei Nejur on November 12, 2016 at 11:26am

Hi Jasper,

Ivy is meant (at least for now) to work with meshes. So 3 and 4 vertex polygons. That being said it does work with ngons (but only flat ones) by treating them as flat clusters of triangles or quads.

1)First you need to triangulate your brep, ngon mesh etc and use Ivy with an angle based weight system for the edges. If you have no preferences on how the individual ngons will remain connected you can just use the standard angle weight system in Ivy.

2)Then use a primary segmentation algorithm, Kruskal for instance.

3)Unroll

4)Use FlatFab and just ignore the (Fl) output of the component.

The way this works is by expanding the tree Graph first in every flat region and only after all triangles in a flat patch are consumed the the tree jumps to another face.

For now you need to have perfect planarity between the faces that triangulate an ngon face. I am releasing an updated version soon that will work with some tolerances considering the way rhino/gh triangulate a some flat surfaces.

I really don't understand the second part of the question. Are you referring to unfolding polylines ?