All vertices are detected as boundary vertices

[EmJay276]

I tried to remesh some models from the Engineering Shape Benchmark (ESB)

For example backdoor.stl from the Flat-Thin Wallcomponents.tar.gz

The result using remesh_botsch is exactly the same as the input.

import gpytoolbox as gpy
v, f = gpy.read_mesh(r"C:\Users\Michael\Desktop\Flat-Thin-Wallcomponents\Flat-Thin Wallcomponents\Back Doors\backdoor.stl")
u, g = gpy.remesh_botsch(v, f, h=None)

I discovered all vertices of the model are detected as boundary vertices by boundary_vertices(f)

But the model has clearly some "inner" vertices (at least on the rounded part in the middle.

[EmJay276]

I've added a PR #69 with a warning in the case of all vertices are boundary vertices.

But I think there is an issue with the boundary_vertices method in this case.

[EmJay276]

I noticed a really weird behaviour, the stl seems to have unique vertices per face (=> the faces are unconnected)
I don't know if this is due to the file or due to the new STL import.

[sgsellan]

Hi @EmJay276 ! Thanks for submitting this issue.

In fact, this is the intended behaviour: an STL file contains no connectivity information, as it just stores a set of individual triangles without any relations between them. So, reading an STL file will return a lot of individual triangles and, since there's no connection between them, boundary_faces will correctly identify all of them as boundaries.

Still, I can see why this is confusing. The easiest thing to do is add a well-documented flag to the stl reader that optionally merges all duplicate vertices (with remove_duplicate_vertices). I believe the boundary will be properly identified in that case.

[sgsellan]

I just pushed an enhancement of our STL read_mesh function to automatically merge STL vertices by default (pushed to. main instead of a PR branch because I haven't had enough caffeine today, it seems haha). Can you confirm this issue is solved and if so, close it?

Thanks for reporting!

[EmJay276]

Thanks for the fast fix! You should get some coffee ☕ 😄
Yes, I think the default behaviour should be to merge duplicate vertices when importing an STL.