Help with modeling_Using just single span surfaces

In my video I purposely showed how both, “Rebuild” and “Offset surface”, failed to do the job they were supposed to do, in order to reveal two known bugs they often do, by making a totally chaotic control point distribution on single-span surfaces with degree 5 and 6 control points. This is why I then I followed those two situations with my workaround that include either the “MoveUVN” tool or a combination of several other commands (“RebuildUV” to 6 control points /limited to degree 3 only/, “Change degree” to 5, and then “Remove knot”) that convert the surface properly and preserve the control point orientation far better than Rhino’s automatic but very buggy tools.

(workflow 1 from video)

  1. RebuildUV will result in a surface Degree 3, 6 CVs in U
  2. Changedegree U = 5 deformable=yes will result in Degree 5, 8 CVs in U
  3. RemoveKnots … Degree 5, 6 CVs (“single Span”)

(workflow 2 - my question)
(Surfaces is Degree 1 U / Extrusion, 2 CVs (“single Span”))

  1. Changedegree U = 5 result: Degree 5, 6 CVs ("single Span)
    what did i miss ?

why are those extra steps above necessary ?

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Usually I leave my History on all the time as I often benefit from having it record certain commands that could be easily edited subsequently (including “Match surface”, despite that I deleted the History on it in this particular video). I avoid using the right-click since it also doubles as a repeat “last command”.

For a linear surface I do not know…


You are right, for straight extrusions with degree 1 and 2 control points in direction it’s enough to change the degree only. I use my workaround with “RebuildUV > Change degree > Remove knot” on all surfaces I want to convert to single span, no matter how many control points they have. Changing just the degree to more dense curved surfaces does not to the job in the same way.

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Yes excatly that is what i am searching for …

Hii Bobi,
Thanks alot for the video. It is very helpful… one can learn alot from. I appreciate your help

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I’m glad to see that it was helpful for you. Again, what I created has some minor errors, so there is still room for improvement. For example, tangency is 0,01-0,02 degrees in certain areas. Achieving perfect 0 degrees requires extra time spent with manual control point manipulation via the sliders of the “MoveUVN” tool.

Wow, seems like I misread your suggestion about the right-click for purging the History for all objects. No idea why I haven’t noticednthat before. I’m a huge fan of utilizing the RMB functionality of the icons. :smiley: Thank you for the suggestion!