Issue with extruding surfaces with gumball in Rhino 7

By October 2021, I was able to extrude and scale individual surfaces in RHino 7 with the Gumball and get an expected result like my picture. But since some time it does not work as expected. The planar extruded surface now have a freeform surface as connection, this is unexpected. See also in my video.
Has there been a fundamental modeling change here or is this a bug?
I would like to continue to get my simple solution expected even from older Rhino versions.
You can find the issue in this videolink: Rhino Issue Extrusion Gumball - YouTube

Hi Klaus - please post a file at the stage before the extrusion that causes the odd surface.


Rhino_Issue_Extrusion.3dm (236.9 KB)
Thanks a lot for your fast feedback.
Find attached an example. At the back, you see the extrusion result. At the front, the 3d object. The “happens” with any object.
You can see my designprocess also in this video:

Hi Klaus - the lower configuration, which is what you have in your file in my image, would produce the result you are getting, the upper one is what is needed to get what I think you want. It is true that older versions of Rhino did not remove the coincident face there when extruding the side surface - in general, presumably the current behavior is preferred but I see that it breaks your workflow.

That said, I am not sure why you are working from surfaces and not a mesh, or for that matter SubDs directly, in box display mode. - the Inset command should let you get what you need in combination with gumball.


Dear Pascal, thank you very much for your quick and competent answer. To work directly with mesh is of course a solution that I will possibly pursue further. My intention is to show my students, who are just in the second week of Rhino, with a simple exercise, what is already possible, if you only work with the Gumball. By pivoting directly to mesh, I hope they won’t then think that the best way to work in Rhino is with mesh… The mesh command inset reminds me a lot of my work with 3ds max. Is there a comparable command or workflow also for polysurfaces/nurbs?

Hi Klaus - My 2 cents worth is that in your place I think I might get the object-types-in-Rhino part over with right up front, and live wirth the consequenses =). Working with surfaces as if they were meshes seems to me to be asking for trouble, and even more in the way of difficult explanations. There is not a good way to consistently use Push-Pull style modeling with surfaces.


nurbs surface inset and offset should be developed

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