Perfect Circle

Hey there,

How do I create an exact circular plane using subd?

Thanks in advance.

Hi Lewis -

You can’t. For exact circulars you need to use NURBS.
-wim

But if you use enough control points , you can get the deviation from a true circle to be so small, that even the center osnap will recognize it as a circle - here’s a triangle fan with 12 segments. Visually you will not be able to tell the deviation, but it’s there - in this case it’s 0.0105mm on a ø100mm circle.


-Jakob

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Or at least I could have sworn that was the case, but it’s not. Sorry for the noise!
-Jakob

This is an example with Grasshopper, you can create subd shape closer to circle but it is not a perfect circle.

subd circle.gh (12.5 KB)

@wim
it would be nice to have some info about the deviation for both

  • deformable arcs / circles
  • subD-Cylinders / spheres …

it would be nice to have the info in the commandline, after starting the command (for current values) or after changing the options
(deformable: degree, Number of CVs)
(sub-D “arround faces”)

for example I imagine entering Degree 5 and 10 CVs for a deformable circle in a document with 0.001 units tolerance, a feedback would be great: maximum diameter within document-tolerance: 500mm.
the inverse info or an adaptive CV-Count would be great as well…
(providing the minimum number of CVs / faces to stay within tolerance)

Hi Jakob - there is a setting for Center osnap locating centers of approximate circles - (Options > Modeling aids) that may effect what happens here, I have not tested on SubDs.

-Pascal

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Are there plans to add weights to subds?

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@oberbichler This would be excellent!