When I compare the outcome of
_Sphere 0 10 _EnterEnd
with
_SubdSphere 0 10 _EnterEnd
I expected to get two spheres of radius 10. Instead, the SubD sphere has the radius of about 8.3.
The vertices of the flat SubD are lie on the sphere with the specified radius.
The more subdivisions, the closer the fit of the smooth SubD with a NURBS sphere.
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I see that, thanks - it’s just that the result is unexpected, and it precludes precision modeling with SubD.
SubD isn’t really intended for precision modelling…
For instance you can’t achieve perfect circles.
As @martinsiegrist already alluded to the measurements you give to such commands work on the control network.
It’s just different…
When I need a precise fit for something cylindrical, I usually subtract a NURBS cylinder.
That should get fixed in Rhino 8 SR3:
https://mcneel.myjetbrains.com/youtrack/issue/RH-75649/SubDSphere-wrong-radius
SubDs might not be able to represent exact circles, but you can still get precise and controlled positions of the limit surface vertices.
RH-79066 is fixed in Rhino 8 Service Release 4 Release Candidate
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