Odd results following the 2018 Y shape tutorial

I was attempting this tutorial

Rhino 3D - Y Shape modelling - YouTube but in WIP7

When I reached the point to convert to SubD I get an odd result. My original Y shape is a valid closed polysurface. The result is all separate open subD parts. Thought suggestions?

Tutorial subd convert.

My WIP7 result at ToSubD

check your input mesh, make sure it’s all joined into one mesh before you convert to subd, it would do this for sure if the mesh is not joined.

It may work to Join all those little ellipsoids after the fact too.


I was under the impression that “_toSubd” could be applied to a Rhino polysurface. Apparently it has to be QuadRemesh-ed first before converting to SubD. Lesson learned.

Hi - Just for what it’s worth…
The help file for this command says:

Mesh, Extrusion, Surface, Sub-surface

So, when you select a polysurface, it takes the individual sub-surfaces of that polysurface as input.

From that same help file:

Sub-surfaces of a polysurface will be converted individually.


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