Controlling creases when converting a joined mesh to SubD

Serengeti (Rhino WIP)
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1

I have a subD that I want to add to using grasshopper. To do this, I first converted to Mesh.

Input SubD
Input SubD1095×912 138 KB
Mesh from SubD
Mesh from SubD1098×910 138 KB

This is a simple example goal: (one simple ring of quads added to each hole in the mesh)
Goal
Goal1040×961 240 KB

When I use Mesh Loft from Mesh+, I get creases at the seams.

Mesh+ creates crease
Mesh+ creates crease1434×697 149 KB

When I extrude the edges of the holes of the mesh as nurbs surfaces and then convert to mesh quads, I get only one ugly creased edge:

brep to mess makes a mess
brep to mess makes a mess1434×696 151 KB

When I use Wombat’s Extrude as Mesh, I get the desired result, BUT according to the panel, the output is “invalid mesh”, and also this limits me to only extrusion, I can’t create lofts and attach them to my starting object:

Wombat Works
Wombat Works1435×696 150 KB

Here is my definition: It requires Mesh+ and Wombat. It has a couple stream filters in it to test methods and test what happens when the mesh through weld and unweld after joining it. I have also tried the crease settings on the SubD from Mesh component in various combinations, and none seem to get me a reliable result. With Wombat and Mesh+, changing the crease settings on the doesn’t do anything, and with a converted brep changeing the crease settings takes it from bad to worse.
Mesh Join and SubD Crease halp.gh (121.6 KB)

How can I reliably control creases when converting joined meshes to SubD in Grasshopper?
If it isn’t possible to have total control now, is there a way to reliably just remove all the creases after joining meshes?

2

I haven’t checked your definition as I don’t have those dependencies. In my experience, these kinds of issues happen you have identical vertices on top of each other. Though there’s often other issues that can creep into your mesh.

Pufferfish’s rebuild mesh can often fix these kinds of problems, especially the weld vertices and identical combine option.

With that said, I’m also curious how others are building out a toolkit for SubD modeling in GH.

3

Thanks, I’ll try the pufferfish component.

One of the obstacles with things like welding vertices in a global operation when working with subDs is that a lot of mesh components triangulate ngon mesh faces whether you want them to or not. We’ll see if pufferfish plays well with Ngons.

4

Rebuild Mesh was somewhat helpful, thanks.

Separate thread about me starting to build my own toolkit for SubD modeling in GH is here: SubD workflow examples for grasshopper: extrude, loft, offset. Also: Questions about creases