What's wrong with this mesh face? (Mesh split)

Lately, I am dealing with a lot of mesh cleaning tasks and ran into all sorts of problems. I got pretty big&nasty meshes to deal with and I can’t work out for myself any best practices.

I wanted to share with you this example where I really got no idea why I can’t split this single mesh face.

Any advice, rules of thumb, other software that you recommend to clean up meshes (mostly 3D scanned data)?

split mesh face problem.3dm (80.7 KB)

Funny, that Grasshopper apparently can split it.

Unfortunately, I can’t use this approach because I am using texture-mapped meshes representing buildings and grasshopper doesn’t hold any texture mapping.

Another problem

I am testing some mesh faces and sometimes faces that can’t be split in the original file, after being copied to another file, they split normally. Note that both files have the same tolerance units.

Instead of working I kept on investigating and found that Mesh trim works far better. There must be some differences inside.
Unfortunately, it makes the process a couple times slower…

  1. I must prepare copies of mesh I want to split into two pieces. Firstly I delete one part, and on the second go, I delete another (from the second copy) and lastly combine results. So, this only makes it twice as long. But that’s not all.

  2. Mesh trim works in a way that I can’t undo any trim while I’m executing the command. From time to time some part won’t trim correctly, resulting in losing too much of a mesh. Then I got to undo command and start one more time. Splitting only one piece at time is a tedious process because I have to: start command, select cutting object (lack of “last used” shortcut inside command), select object to trim.

So I can gamble or accept this process:

start command, select cutting object, select object to trim, start command, select cutting object, select object to trim, start command, select cutting object, select object to trim

  1. Window selection not working with Mesh trim command also makes it slower. so even if there were no nr. 2, I got to click, click, click, click

I find that if you change tolerance to 0.01 unit (down from original 1.0 unit in your file) MeshSplit works just fine.

Ah, this one from the file was a coincidence. I changed two things at the time and missed it…

However, in the video, you can see an example where the same geometry doesn’t split in my original big file (tolerance set to 0.01 cm) and copied into a new file, (with the same tolerance) it splits fine. Unfortunately, I didn’t save this piece to share file with you.

I did not watch the first video:

I hope that this is not the same for all of my videoes posted on the forum, because I am posting a lot of them, they are working just fine on my pc, and I use standard discourse tool to upload them. Can you please check my other videos?

Anyway, I got one more single mesh face which I can’t split with Rhino’s Mesh split (but I can trim) regardless of my unit tolerances. (Grasshopper Mesh Split works fine)

split.3dm (1.2 MB)

I use meshlab to clean up scans.


Unfortunately some scans are terrible.

Sometimes if the scan can be repaired enough, then using rhino 7 quadremesh on it can help sometimes to bring order to the mesh.

In Rhino 7 we also have completely re-written the mesh intersector, so it is always worth a try. When re-writting an intersector we always hope it is better, but takes a lot of testing.

In this case your original model splits just fine with 7 WIP:

And the split.3dm example above also works.

Amazing! It split now after I downloaded my own file because I could not believe it.

But hey, I uploaded video proof showing that it wasn’t working!

You can see that I can’t split it by Mesh Split and I am receiving info:
1 meshes were split into a total of 0 meshes.

Am I going crazy? :grimacing:

I am using the newest Rhino 7 WIP. I used your files


Files directly.

It might be that the Rhino 7 upcoming this week has this. It clearly did not work in Rhino 6.

One potential trouble is the mesh density in the large surfaces could be a problem. Rhino 6 was very sensitive to mesh settings when trying mesh split.