toSubD does not inherent CP structure with Deg 3 surfaces

[CJ_DE (CJ)]

ToSubD does not turn NURBS surface control points into SubD control points with Degree 3 NURBS surfaces. It does work above and below deg 3?!
Rhino Version 7 SR13

any suggestions?

[theoutside (Kyle Houchens)]

I am seeing the same thing here- Looks buggy to me. I’ll write it up-

https://mcneel.myjetbrains.com/youtrack/issue/RH-66584

[pascal (Pascal Golay)]

Hm… that does seem incorrect - if the surface is not flat it seems to get it right. For now, ExtractControlPolygon then ToSubD the resulting mesh.

-Pascal

[CJ_DE (CJ)]

top… thx

[eddi]

@CJ_DE

ToSubD does not turn NURBS surface control points into SubD control points with Degree 3 NURBS surfaces

@theoutside

I am seeing the same thing here- Looks buggy to me

I do not agree, same as in TSpline, has always been this way !
Srf(rigid flat) rule Degree3 / UV = CP 4 = SubD 1 Face,
Srf(rigid flat) rule Degree3 / UV = CP 5 = SubD 4 Faces
ect …
Base for SubD is allways degree3 and other than degree3 must by internally converted.
Accordingly it leads to the other topology.

[CJ_DE (CJ)]

but it works in former versions like shown in Phil Cook`s tutorial

An Introduction to SubD (Subdivision Surface Modelling) in Rhino3d v7

[eddi]

Throw a few seconds here

T-Splines training 06 - signet ring

Exception forms when the surface is curvy,
At the beginning and end the faces are divided.

[CJ_DE (CJ)]

from the docs:

UseSurface

ControlPoints

Turns NURBS surface control points into SubD control points.
Use this option if you are doing “Class A” modeling and need to join separate SubDs into a single SubD.

Location

The output SubD has the best fit to the input NURBS surface. Extra faces might be inserted.

[eddi]

@CJ_DE

Turns NURBS surface control points into SubD control points.

Yeeh Srf with uv rigid is enough to raise one CP to mimicron and it works

@CJ_DE

“Class A” modeling

Hmm with flat surface does this make sense ?