Hi all, I am completely new to Rhino, I am a CAD user and work in the Built Heritage. I have been asked to draw/digitize on Rhino, some mesh models (obj) representing historic ship timber. I am using the polyline-on-mesh tool, but I have a big issue. I have turned off all snaps and smartTrak, but the line is still not ‘free’ and it seems to snap to the mesh’s vertex, so I cannot produce a nice 3D model. Is there anyone that use the tool often and can give me advice on how to solve this problem and draw with the polyline on mesh without constrictions?
Hi @Sara_Marandola
Welcome to where the Rhino roams 
I’m not seeing any initial problems with PolylineOnMesh here, so it might be a setting somewhere. Just to check: Have you de-selected/turned off all of the osnaps, or have you disabled them entirely? Same question for Sub-objects? Also, run the SystemInfo command in Rhino and post the result here.
HTH, Jakob
HI jacob! Thank you for your support.
Yes, I have disabled all osnaps entirely, and I attach here the SystemInfo.
Rhino 8 SR29 2026-3-4 (Rhino 8, 8.29.26063.11001, Git hash:master @ bbd126f84fcdaf7a974615b7c9f4f8667571c147)
License type: Evaluation, build 2026-03-04
License details: Cloud Zoo
Expires on: 2026-05-14
Windows 11 (10.0.26200 SR0.0) or greater (Physical RAM: 64GB)
.NET 8.0.22
Computer platform: LAPTOP - Plugged in [100% battery remaining]
**Hybrid graphics configuration.
Primary display: Intel(R) UHD Graphics (Intel) Memory: 1GB, Driver date: 12-9-2023 (M-D-Y).
Integrated graphics device with 4 adapter port(s)
- Windows Main Display is laptop’s integrated screen or built-in port
Primary OpenGL: NVIDIA GeForce RTX 4090 Laptop GPU (NVidia) Memory: 16GB, Driver date: 5-14-2025 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 576.52
Integrated accelerated graphics device with 4 adapter port(s)
- Secondary monitor is laptop’s integrated screen or built-in port**
OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
GPU Tessellation is: 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: 5-14-2025
Driver Version: 32.0.15.7652
Maximum Texture size: 32768 x 32768
Z-Buffer depth: 24 bits
Maximum Viewport size: 32768 x 32768
Total Video Memory: 16376 MB
Rhino plugins that do not ship with Rhino
Rhino plugins that ship with Rhino
C:\Program Files\Rhino 8\Plug-ins\Commands.rhp “Commands” 8.29.26063.11001
C:\Program Files\Rhino 8\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino 8\Plug-ins\RhinoRenderCycles.rhp “Rhino Render” 8.29.26063.11001
C:\Program Files\Rhino 8\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 8.29.26063.11001
C:\Program Files\Rhino 8\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino 8\Plug-ins\MeshCommands.rhp “MeshCommands” 8.29.26063.11001
C:\Program Files\Rhino 8\Plug-ins\RhinoCycles.rhp “RhinoCycles” 8.29.26063.11001
C:\Program Files\Rhino 8\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 8.29.26063.11001
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”
Hi @Sara_Marandola
The only thing that might be a wee bit off, is the age of your graphics card driver - it could probably do with an update. Other than that, you might have to post a file and describe what you are seeing (and what you were expecting to see). I’m attaching a quick video of what PolyLineOnMesh looks like here, just for comparison. From your description, I’m guessing that your cursor snapping to the vertices as you move across the mesh - strange indeed.
-Jakob
PS I just realized I did the screen recording from WIP of Rhino9, but it’s the same in R8.
Thank you Norman, from the video you sent, I think I understand now that what I see as a problem, it is actually not an issue but the way the software works: the ship timbers are extremely irregular and rounded, and when I trace a polyline, this adheres to the surface and appears snapping on points far away (from a 2D perspective), but it actually follows the irregular profile of the object. I will update my graphic card drivers.
If you don’t mind, I will come back to you later in the day just to show the final result of what I did and see if you can give your opinion on that.
Thank you very much!
Hi @Sara_Marandola
You’re always welcome back! Also you might just try and explain what you are trying/hoping to achieve (in screengrabs, sketches, words etc.). There might be a way to achieve what you are looking for
Kind regards, Jakob
@Sara_Marandola If you need 2D sections of a mesh, use Section command to create a single section, or Contour to create equally spaced parallel sections.
Thank you David, I defently will use these commands for secrions and profiles.Thanks a millioin. Sara