Why are my curved extrusions going straight line?

[Joe4 (Joe Babb)]

Doing an ornamental gate design where I create closed, planar outlines and then extrude them for a perspective view. When I first do them everything is fine, then sometime later they show up as straight line segments. This is a very recent thing and hasn’t happened to me as far as I know in all the years I’ve been doing this. In the picture below you can see the curved lines below the spears but the “funny” extrusion below. I can exit the program and restart it and they go away but some other extrusion may go straight. What’s going on?

Rhino 8 SR24 2025-10-8 (Rhino 8, 8.24.25281.15001, Git hash:master @ ba28668a8431990c700173e46ef2dbcb873cf092)
License type: Commercial, build 2025-10-08
License details: Cloud Zoo

Windows 11 (10.0.26100 SR0.0) or greater (Physical RAM: 31GB)
.NET 8.0.21

Computer platform: DESKTOP

Standard graphics configuration.
Primary display and OpenGL: NVIDIA GeForce RTX 3060 (NVidia) Memory: 12GB, Driver date: 9-5-2024 (M-D-Y). OpenGL Ver: 4.6.0 NVIDIA 561.09

Accelerated graphics device with 4 adapter port(s)

• Windows Main Display attached to adapter port 0

Secondary graphics devices.
AMD Radeon™ Graphics (AMD) Memory: 1GB, Driver date: 1-11-2024 (M-D-Y).

Accelerated graphics device with 5 adapter port(s)

• There are no monitors attached to this device!

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: 9-5-2024
Driver Version: 32.0.15.6109
Maximum Texture size: 32768 x 32768
Z-Buffer depth: 24 bits
Maximum Viewport size: 32768 x 32768
Total Video Memory: 12 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” 8.24.25281.15001
C:\Program Files\Rhino 8\Plug-ins\rdk.rhp “Renderer Development Kit”
C:\Program Files\Rhino 8\Plug-ins\RhinoRenderCycles.rhp “Rhino Render” 8.24.25281.15001
C:\Program Files\Rhino 8\Plug-ins\rdk_etoui.rhp “RDK_EtoUI” 8.24.25281.15001
C:\Program Files\Rhino 8\Plug-ins\NamedSnapshots.rhp “Snapshots”
C:\Program Files\Rhino 8\Plug-ins\MeshCommands.rhp “MeshCommands” 8.24.25281.15001
C:\Program Files\Rhino 8\Plug-ins\RhinoCycles.rhp “RhinoCycles” 8.24.25281.15001
C:\Program Files\Rhino 8\Plug-ins\Toolbars\Toolbars.rhp “Toolbars” 8.24.25281.15001
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”

Dewitt-Gate-Draft-250411.3dm (13.2 MB)

[Tom_P]

@Joe4

then sometime later they show up as straight line segments.

this looks like a display / Mesh issue.
looks fine here on a first fast view:

update your system
update your graphic card drivers (Driver Date: 9-5-2024)
update rhino

maybe update the render mesh settings for the file
_documentProperties → mesh → …

or set custom render mesh for the objects (under properties panel) where the file-setting does not fit.

hope this helps - kind regards -tom

[Joe4 (Joe Babb)]

Looks like updating graphics driver helped. We’ll see. It was intermittent.

[Joe4 (Joe Babb)]

Still getting it even after updating driver.

sure hope somebody can figure it out.

If I close Rhino and re-open the file it seems to go away. Maddening.

[JimCarruthers]

It’s just the render mesh. Change the mesh settings.

[Joe4 (Joe Babb)]

okay, help me out. I’ve been using Rhino since version 6, and I haven’t run into this problem until now. The picture I sent is shaded view. I’ve looked in Tools-Options- and don’t see or understand what I need to change. It’s also intermittent. Please give me a more complete hint.
thanks,

[Lagom]

Most peculiar. Looks good right upon opening. Rhino Version 8 (8.23.25251.13002, 2025-09-08)

[JimCarruthers]

In the Options dialog, go up toe “Document Properites” then to “mesh”…there is lots of info on the different settings… Rhino Mesh Settings [McNeel Wiki]

[Joe4 (Joe Babb)]

I can see that it will take some time to figure out how to adjust this or whether it is something I’m doing.

[JimCarruthers]

It’s just the render mesh nothing is “wrong” with the model. I mean the file looks fine when I open it so I don’t know what’s up with that, but those durned ‘extrusions’ seem to have their own mesh settings can can look very rough sometimes, but whatever’s going on with the render mesh unless you actually have some sort of bad geometry interfering with proper meshing the problem is NEVER with your model.

[wim (Wim Dekeyser)]

Hi Joe -

@Joe4

I’ve looked in Tools-Options- and don’t see or understand what I need to change. It’s also intermittent. Please give me a more complete hint.

I only see one 3dm file attached in this thread and that looks like an earlier version of your last picture.

At any rate, when I open that file and look closer at some of the details, this is what I see:

As Jim hinted, those are extrusion objects.
Selecting a few of those and running ConvertExtrusion gives me this:

This should work fine with extrusion objects also, though. When I use a curve in your model and make a new extrusion object, that one displays fine.

I then switched the mesh settings from the current “Smooth and slower” option to “Jagged and faster” and that immediately made everything look much better. Then switching back to “Smooth and slower” made it look better still.

Somehow, your objects appear to have gotten stuck with some mesh setting that clearing the meshes and then rebuilding them does not solve. Switching between the settings clears that up.

I’m not able to reproduce getting in such state and if you find a way to do so, please let us know.
-wim

[Joe4 (Joe Babb)]

I also played with mesh settings and seemed to have same experience as you. I still don’t understand why this has popped up now. My workflow hasn’t changed and I’ve been doing this sort of thing for a long time without this problem. The drawing file size has gotten pretty large at 26Mbyte and I’m not sure why that is, but it shouldn’t cause a problem.

[Joe4 (Joe Babb)]

This might not be so problematic if I could fix it and it would stay fixed. But this morning I’m back to square 1, opening the file and finding more of the same problem. Grrr So the problem isn’t solved.

[JimCarruthers]

So you actually see rough meshes when you open this file? I don’t. In 8 or 9. Could the presets have gotten messed up?

[3dsynergy]

Hi All and @Joe4 @wim

There must be a bug in the mesh settings in properties and then the display not doing anything, I opened this in V7 and setting various mesh settings does nothing. In all display modes. Nothing happens. I think this needs to be looked at by Jeff or who ever is in charge. It looks like there is a zoom mesh problem going on and the fact that no mesh settings changes anything in V7 seems to say this is broken.

Edit:
Ok I looked at this again and I see that zooming in to the top bar you can see the meshing though looking good from far is far from good and doesn’t follow the input curves. Also I think something is bugged in the custom mesh settings in V7, in that using the slider doesn’t do anything going either coarse or fine. But adjusted only the angle value does, the default is set to 20 degrees and seems high to me I had to go to .5 degrees to get the angle to duplicate the curve when zoomed in.

I think it’s a compromise bug in the meshing of Rhino in that meshing for display is bugged in many ways, either with this bug where it comes back intermittently or meshes losing their shading, losing texturing and or turning black. Also curves are not drawn as clean as could be so I think this is a compromise done by the developers to increase redraw speed.

RM

[Lagom]

This is really odd. Opening the file in macOS V7 and macOS V8 after opening Rhino and doing nothing else looks fine as I depicted above. A Windows “under the hood” settings thing, perhaps?

[Joe4 (Joe Babb)]

I don’t pretend to know what the problem is. But it is intermittent and after I fix one element by changing mesh settings or deleting and re-extruding, another one may show up bad, or else coming back to work the next day and opening the same file finds the ones I fixed bad again. I can’t imagine what it is about this one file. I’ve opened up some old files and they look fine. If I can get the problem to be consistent, maybe I can figure it out.

[jeremy5 (Jeremy)]

Hi Joe,

For some reason your render meshes are a mess. To fix things do this in your troublesome file:

1. Set the mesh properties back to default for the ‘Smoother and slower’ settings. The detailed settings should then look like this:
   

   

2. Use _SelExtrusion to select all the extrusions.

3. In the Properties panel, tick Custom Mesh, then untick it. This will reapply the default mesh settings to all the extrusions.
   

   

4. Save your updated file.

HTH
Jeremy

[Joe4 (Joe Babb)]

This seems to have fixed it. I’ve been here before so we’ll see what happens over the next few days. Funny thing about that file. I looked at other files and they had the settings you recommended. And when I clicked on Restore Defaults the numbers you showed did not come up, so I ended up putting them in manually. I would never have thought of the step of selecting all the meshes, going to their properties, and clicking then un clicking Custom Mesh. Rhino is powerful, but complex. Good thing we have the forum. Many thanks for your help.

Joe

[Joe4 (Joe Babb)]

Well, I spoke too soon. It’s doing it again this morning. I checked the mesh settings and they appear to be okay as far as I can tell.

Can’t upload the current file ‘cause it’s too big. What happens if I save it small? Would it lose too much information?