Faulty Simplify Quadric Decimation since 0.18.0. 0.17.0 seems to work more reliable.

[limpbot]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for main branch).

Describe the issue

Using 0.18.0 simplify_quadric_decimation does not reach the target_number_of_triangles reliable for the given not watertight mesh. In 0.17.0 this works reliable.

Probably related to #6163 .

Steps to reproduce the bug

import open3d

mesh = open3d.io.read_triangle_mesh('not_watertight_mesh.ply')
print(mesh)
mesh_decimated = mesh.simplify_quadric_decimation(target_number_of_triangles=mesh_vertices_count)
print(mesh_decimated)

Error message

Expected behavior

No response

Open3D, Python and System information

- Operating system: Ubuntu 22.04
- Python version: Python 3.10
- Open3D version: output from python: 0.18.0
- System architecture: x86 
- Is this a remote workstation?: no
- How did you install Open3D?: pip

Additional information

No response

[limpbot]

not_watertight_mesh.ply.tar.gz

[ssheorey]

@bjudeworley can you take a look at this? Thanks!

[bjude]

I'll try and take a look but I now have a 3 month old so my free time is basically nil so it might be a while.

If I had to guess, the 0.17.0 output probably has one of the bad element types my PR aimed to fix, or requires generating them at some intermediate step in the decimation process. Maybe take a look at the output mesh in something like Meshmixer and see if that's the case.

@limpbot, your example doesnt have enough info, what is the value of mesh_vertices_count?

[limpbot]

hi @bjude, thx for taking a look. The vertices count should be 7055, and the faces count should be 15670.

[bjude]

@limpbot can you re-upload the mesh, its 404'ing when i try and download it

[limpbot]

Sorry, I have also problems loading it currently. Will reopen if I find another example