Polysurface to Mesh to Subd Trouble

Hi there, I’m new to Rhino but not to 3D modeling as a whole. Recently, I’ve been trying to figure out organic modeling & architecture.

Here in this file, I have a polysurface of a poly surface of a part of a design, but when I convert it into a mesh and then use the TosubD command it turns into a porcupine. (re-applies many extrusions and steps I previously completed is what it looks like to me)

I’ve searched on old posts that this has to do with trimmed and untrimmed surfaces or something, is there a way to fix it? At this point I don’t care about deviation from original model parameters.

Warning it’s a pretty big file - includes both the original polysurface I made and the mesh I derived from it.

Do I have to start over? Is there any other way to ge that “smoothed” look that subd gives?

Hello - you may want to QuadRemesh then convert to a SubD.


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Hi there, thank you for your answer.

One problem though: The Quad mesh command gets stuck at either 70% or 75% no matter if I input the polysurface or the mesh.

If you run the diagnostic Check command on your mesh you should see several issues (such as intersecting faces) which may give you problems downstream.

So I took your polysurface as a starting point for some quadremesh experiments. On my laptop with 16GB memory I couldn’t complete a quadremesh in a reasonable time. But by using wirecut to split your model into three tiers I could quadremesh each of tthem successfully. Trying to convert the three new meshes into subd took all night and when completed there were severe spiky distortions.

Trying on another computer with 64GB memory I could quadremesh the whole piece reasonably quickly using the default target quad count of 2000, but there were significant distortions in the meshing of some of the limbs within the structure. A second attempt with the target quad count increased to 20000 ran till the completion was 95% but I canned it after half an hour (I’ve got my own model to work on!).

So it looks like there may be workarounds, like splitting the model, but no straightforward solution.

How did you create the original model? Do you need to have the result in Rhino?

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Hi there,

Thank you for your answer and your time. I will try the steps you mentioned.

The model was created all in Rhino, starting with stacking a few cylinders, of which I then unioned, shelled to get just the outer layer, added fillets, and then used the InterpCrvonSrf command to “draw” on the irregular holes you see on it. I then extruded the curves drawn (took a long time as I had to manually change the direction of each extrusion), used boolean Splt to “cut” into the overall shape, and deleted the extra resulting pieces.

I would like to work on this in Rhino, but at the moment I am just looking for the “SubD” kind of looks, so basically no edges, smoothed, and polished kind of. I’d be happy if any other program can achieve such a look without sacrificing much accuracy or quality. I’m experimenting with Blender, but I don’t have much experience in modeling so it’s going slow.

Do you know of any way to get the effect I’m talking about without having to brute force through this current quad mesh and subd trouble?

So, in a further experiment, I was able to quadremesh with these settings:

And create a subd with these:

The quadremesh has an obvious spike but I figured this would be easier to fix as a subd.

This was done on a machine with 64GB of memory. The file is too big to upload, but here’s an image:


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Thank you so much for dedicating even more of your time to my problem. I really appreciate it.

I guess more ram answers a lot of questions in Rhino? I’ll experiment with some other ways to get the desired effect. The output looks about what I expected, if not a little twisted.

Thank you for all your help. I’ll mark this topic as solved.



I guess it’s relevant for manipulating large meshes like yours but most of the time I can work happily within the limitations of my laptop which only has 16GB, if I need to.