Joining curves changes their geometry

Rhino Rhino for Windows
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1

I am using Rhino 8 version SR4 on Windows. I am noticing that when I join certain curves, the geometry of the resulting joined curve is altered slightly:

I have tried exploding everything first, as well as using the convert command. This seems very minor, but I want to be able to join curves knowing that everything stayed exactly where it was before the command. Any thoughts:

System info:

Rhino 8 SR4 2024-2-6 (Rhino 8, 8.4.24037.15001, Git hash:master @ bee9cb852c752350676ca6bc7f3f6946b5bbc6b7)
License type: Commercial, build 2024-02-06
License details: Stand-Alone

Windows 11 (10.0.22000 SR0.0) or greater (Physical RAM: 32GB)
.NET 7.0.0

Computer platform: DESKTOP

Standard graphics configuration.
Primary display and OpenGL: NVIDIA GeForce GTX 1050 Ti (NVidia) Memory: 4GB, Driver date: 10-18-2023 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 537.70
> Accelerated graphics device with 4 adapter port(s)
- Windows Main Display attached to adapter port 0
- Secondary monitor attached to adapter port 1

OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
Redraw scene when viewports are exposed: On
Graphics level being used: OpenGL 4.6 (primary GPU’s maximum)

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

Vendor Name: NVIDIA Corporation
Render version: 4.6
Shading Language: 4.60 NVIDIA
Driver Date: 10-18-2023
Driver Version: 31.0.15.3770
Maximum Texture size: 32768 x 32768
Z-Buffer depth: 24 bits
Maximum Viewport size: 32768 x 32768
Total Video Memory: 4 GB

Rhino plugins that do not ship with Rhino

Rhino plugins that ship with Rhino
C:\Program Files\Rhino 8\Plug-ins\Commands.rhp “Commands” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\WebBrowser.rhp “WebBrowser”
C:\Program Files\Rhino 8\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino 8\Plug-ins\RhinoScript.rhp “RhinoScript”
C:\Program Files\Rhino 8\Plug-ins\IdleProcessor.rhp “IdleProcessor”
C:\Program Files\Rhino 8\Plug-ins\RhinoRenderCycles.rhp “Rhino Render” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\RhinoRender.rhp “Legacy Rhino Render”
C:\Program Files\Rhino 8\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino 8\Plug-ins\MeshCommands.rhp “MeshCommands” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\RhinoCycles.rhp “RhinoCycles” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\RhinoCode\RhinoCodePlugin.rhp “RhinoCodePlugin” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 8.4.24037.15001
C:\Program Files\Rhino 8\Plug-ins\3dxrhino.rhp “3Dconnexion 3D Mouse”
C:\Program Files\Rhino 8\Plug-ins\Displacement.rhp “Displacement”
C:\Program Files\Rhino 8\Plug-ins\SectionTools.rhp “SectionTools”

File:

EMER_023_JOIN PROBLEM.3dm (2.4 MB)

Thanks!

2

Seems like your tolerances are too low for the size of the features you’re working on. I’d try bumping them up to .0003" or something like that.

3

Hi Ben, I’d also consider replacing the junky overly complex parts of the curve there with a clean and simple one like a blend curve.

image
image706Ă—696 48.9 KB

-Pascal

4

@phcreates I believe this solved it, thank you.

@pascal also a valid solution, thank you.

5

Please mark solution so others like me do not need to read the topic. Thanks

6

@Ben_Schmanke - my comment was not to fix the join problem, the tolerance is the issue there, but just as a generally good thing to do when the curves are this messy.

-Pascal

7

This looks like a bug. There is no reason for Rhino to be changing the curves
This has nothing to do with tolerance or how junky someone thinks your curves are.
This is just a bug it should not happen , at least without the informed consent of the user.

Since when does Rhino think its proper to join an open polyline with 20 points to a open polyline with 31 points and get a open polyline with 42 points?
On what basis is McNeel deciding to redesign those curves?

The help for join states :
" Degrees and control points will not change when curves with different degrees are joined."

1 Like