Is this normal? I think a bug. update: no bug but user error

three times the same screen. the only difference the first is just the selected edge. the second is the edge moved the first time, the third is the same edge moved again, without changing selection or anything else.
The direction I changed both times was dragging the red arrow of the gumball. no deselect or select anything.
I hope you understand what I am trying to say, Sorry for my bad english

Rhino 6 SR21 2019-12-17 (Rhino 6, 6.21.19351.09141, Git hash:master @ 4d373f64ffb55e3a8d607d9618590728d86fb1e9)
License type: Educational, build 2019-12-17
License details: Stand-Alone

Windows 10.0 SR0.0 or greater (Physical RAM: 16Gb)
Machine name: FRITS-LAPTOP-HP

Hybrid graphics system.
Primary display: Intel® HD Graphics 530 (Intel) Memory: 1GB, Driver date: 10-17-2017 (M-D-Y).
Primary OpenGL: NVIDIA GeForce GTX 960M (NVidia) Memory: 2GB, Driver date: 11-20-2019 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 441.41

OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
Redraw scene when viewports are exposed: On

Anti-alias mode: 4x
Mip Map Filtering: Linear
Anisotropic Filtering Mode: Height

Vendor Name: NVIDIA Corporation
Render version: 4.6
Shading Language: 4.60 NVIDIA
Driver Date: 11-20-2019
Driver Version:
Maximum Texture size: 16384 x 16384
Z-Buffer depth: 24 bits
Maximum Viewport size: 16384 x 16384
Total Video Memory: 2 GB

Rhino plugins
C:\Program Files\Rhino 6\Plug-ins\Commands.rhp “Commands” 6.21.19351.9141
C:\Program Files\Rhino 6\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino 6\Plug-ins\RhinoRender.rhp “Rhino Render”
C:\Program Files\Rhino 6\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 6.21.19351.9141
C:\Program Files\Rhino 6\Plug-ins\rdk_ui.rhp “Renderer Development Kit UI”
C:\Program Files\Rhino 6\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino 6\Plug-ins\rhinocam\RhinoArt1FileExporter For Rhino6.0.rhp “RhinoArt1FileExporter”
C:\Program Files\Rhino 6\Plug-ins\RhinoCycles.rhp “RhinoCycles” 6.21.19351.9141
C:\Program Files\Rhino 6\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 6.21.19351.9141
C:\Program Files\Rhino 6\Plug-ins\3dxrhino.rhp “3Dconnexion 3D Mouse”
C:\Program Files\Rhino 6\Plug-ins\Displacement.rhp “Displacement”

yes, it happens when you try to drag an edge of a trimmed cylinder, to avoid that you can extract the surface and use ExtendSrf and then join again.

it is strange because with the second drag the problem solves itself and occurs no further.
The file saved and opened in WIP7 give the same result.

Hi Frits - a quick test in Rhino 7 doesn’t show that issue here.
That said, I can’t generally recommend to use that workflow on objects with some complexity.

2020-01-20 MoveEdge

Even if the objects appear to survive the operation, make sure to check the wireframe to see if it hasn’t become overly complex - as it did in that second move in this screen grab.
I’m not sure why that GIF is reduced to 50x29… Attaching it here as a zip file as well in case someone is interested…

2020-01-20 (5.6 MB)

I proberbly do not understand what you are writing but the wireframe has no weird lines and is very simple.

What I did to make the object can you see in the description Y section tube
In this post I answered how I have made the Y section tube.
Did I do there something wrong?
Finishing that object I wanted to shorten it a bit and then I saw the strange view.
With analyze / Diagnostic the polysurface is valid

Hi - I guess I should have written “Isocurves” instead of wireframe. You have modified your wireframe display mode to only see the edges. A default Shaded display mode will also tell you if your objects are more complex than what they need to be, as in this picture from your other thread:

As long as those isocurves are simple after moving an edge, all is fine. If they start looking like the following, you better do as Diego wrote and extract the surface which edge you want to move.


Ohhhhh, now I understand. Yes with the isocurves on, the object changes a lot while moving the edge. Thanks for explaining. I shall figure out what diego is trying to tell me. update, I understand what he was telling me. in short: cut the part if to long and add a part if to short.

That will add a new surface and (might ()) result in a visible seam where you add the part:

That is a perfectly fine solution if you don’t mind that seam. (
) If you turn off “Show tangent edges” in your display mode, this edge won’t even be visible.

What Diego wrote, however, is to use the ExtractSrf command to take the surface that is too short out of the object. Then use the ExtendSrf command to make that surface longer. Finally, join this longer surface with the rest of the object.


Wim, THANKS for explaining the lesson Diego offered me.

I am grateful for the help given by the both of you

Sorry for my bad english, it is not my native language

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