Subd Sweep Commands create over sized sweeps

Just a quick issue I am having with the SubD sweep 1 and 2 commands.

When I lay out curves for a simple shape to follow, if creases are selected the sweep creates an over sized shape.

For example, if I lay out a ring to be swept 2mm by 2mm, the end result was 2.3mm.


Anyone know how to avoid this? Subd is pretty fantastic. This little “feature” is a bit annoying, though.

Hello - what happens to the small curve if you MakeSubDFriendly?


It rebuilds the curve a little strangely, and I can no longer check the “subd creases” command.
In this case I can work around by just using the SetPt command.



This one is after setting the points.

Also, Thanks for the new command :slight_smile:

Hello - Does a section through the original sweep match the ‘friendly’ curve?


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Not exactly, I have to redraw the curve once I make it friendly.

If I leave it as is directly from “Makesubdfriendly” It redraws the curve to that weird shape in the previous message.

Hi @perrasjewellery

What I see is that If you draw the ring profile as periodic curve, that curve will be natively SubD Friendly.
Then you have a chance to not face the described behaviour when using Sweep 1 ( Right on the picture )

Ring profiles; depending on the drawing strategy applied, are often composed of a set of curves of varying degree ( left on the picture - 2 lines of D1 + 2 curves of D2 or 3 )
Converting these curves without impacting the shape sometimes leads to a compromise.

In my humble opinion, in some situations, I find more relevant to draw a ring profile in a specific way that better correspond to the needs instead of trying to convert an object to match the needs.
…which often leads to unwanted complexities or extra modelling steps.

I think it would be useful to have an option allowing to better manage the resulting curve structure while running the command MakeSubDFriendly.

Hope it helps.

Rodolfo Santos

Thanks so much.

In this case the profile was pretty simple to fix, but had I not checked that it could have been messy when it went off to the client as a fatter ring.

This profile was fairly basic, had it been more complex this could be a problem. I’ll be much more aware in the future of how this behaves.

Thank you for the detailed explanation and your help.
Thanks to pascal also.


Hi Colin - please post the inputs to the sweep that turns out wrong and we’ll take a look.


Not quite sure how you would like me to post them. exported as a .3dm file?

Hello - yes, please, as a 3dm file. If there is a bug there, I want the developer to see it.


Here are the curves.

The commands used were Subdsweep1 and Subdsweep2.
But resulted in the oversized object.

Using the “Makesubdfriendly” command transformed the profile curve into the wonky one as above.

Thank you so much for looking into this.


Subdsweep issue.3dm (137.2 KB)