FlowAlongSrf unwanted result

I want to “unroll” a mesh.
FlowAlongSrf seems to be the way to go.
It kind of works, but the result is wrong.
The resulting mesh is closed on one side, exploding doesn’t help.
I expect the mesh to be the same as the round shape, only flat.



This is what I do:

And the file:
2024-06-05_Flow.3dm (10.2 MB)

It’s the same result in V7 and in V8.
What can I try?

I now see there is an overlap in the source mesh.
I made a new mesh without the overlap, but the flat result is the same.

Hi @Charles
It’s a bad mesh. Non-manifold edges, bad faces etc. I think it’s primarily near the seam - without examining it closely, it looks wonky. Clean up the seam area and it should work.

HTH, Jakob

Thanks Jakob.

In the meantime I made a good mesh:
2024-06-05_GoodMesh.3dm (9.0 MB)

Same result with FlowAlongSrf.

The good mesh has some open edges at the seam:

Up to now I was not able to close them.
I closed them using _AlignVertices.
So the mesh should be really ok now.

The result is not.

Hi @Charles
Since the mesh is, as you mention, still closed at the seam, that single row of mesh faces is stretched when you run FlowAlongSrf. To split the “flat” mesh and the mesh you need, run Unweld with a low angle, eg. 5 or 10, and then Explode. Now you should be able to delete the flat top.
HTH, Jakob

Thanks for your input Jakob.

Kind of works using Unweld and delete, it also works using sub-object selection at the ends and delete.
Cumbersome and not logical to me.
Especially as this is a simplified test case, in reality the round mesh is a scan.
The must be a method to open the round mesh.
I had success by cutting a gap in the mesh - then the result is ok.

Now I had an idea:

BTW, I can see the splitting doesn’t work ok…

Interesting, the half mesh fills the complete target surface, but only the offending parts.

I’m able to get a result by workarounds.
I still think something is not correct with FlowAlongSrf.

I would recommend to skip the 360 degree approach.
There will always be problems close to the seam.

do two surfaces, two meshes for each 180 degree / half of the rotation.

if you want to stay with the 360 degree apporach - do a gab that is smaller then your production tolerance, but much bigger then the document Tolerance.
the basic concept will look like this:

(but the gab will - for example - only be 0.01 mm)