Invalid tetra in TetraMesh when creating TriangleMesh with alpha shapes

[NicoBux]

When using #1621 work around for creating TraingleMesh from a point cloud with 'TriangleMesh.create_from_point_cloud_alpha_shape()', I get the following error:
[Open3D ERROR] [CreateFromPointCloudAlphaShape] invalid tetra in TetraMesh

To Reproduce

1. Create point cloud by manually creating PointCloud() object, then adding in points from a Vector3dVector()
2. run:
   alpha = .03
tetra_mesh, pt_map = o3d.geometry.TetraMesh.create_from_point_cloud(pcd)
mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha, tetra_mesh, pt_map)
3. See error

Environment (please complete the following information):

• OS: [Windows 10.0]
• Python version: 3.6.7
• Open3D version: 0.9.0.0
• Is this remote workstation?: no
• How did you install Open3D?: conda

[griegler]

Maybe visualize your tetra mesh and the point cloud. Probably there is a tetra that has a triangle with zero area? The problem is here that results in a 0 and would lead to a div by 0.

[LyceanEM]

I have experienced the same problem, with the same python version and Open3D version. Is there any way to work around this at present?

[NicoBux]

@griegler Unfortunately I am not able to visualize any type of Geometry. I get an error like Invoked with: geometry::TetraMesh with 5481 points and 34003 tetrahedra. When using o3d.visualization.draw_geometries(tetra_mesh). This happens with pointclouds. Is there another way to filter and remove zero-area tetra?

[griegler]

@buxbomber Is it possible to share a point cloud where this problem happens?

[NicoBux]

@griegler Oh jeez I did not realize draw_geometries() required a list as argument. The visualization works fine. However, I still am unsure on how to clean up the tetra_mesh.

Edit: Here is a point cloud: https://drive.google.com/open?id=1wybuC6wdLL4Qx8iBuyXij4gajZ_MY7_k

[lschfr]

got the same problem with Open3D 0.10.0.1, Python 3.7.4, Windows 10 and a tetra-mesh built out of a point-cloud

[jaredbaggen]

Also have the same problem, Open3D 10.0.1 Python 3.8, Mac 10.15.6.

[Wuestengepard]

I also have this Problem. Drawing the Mesh and Pointcloud results in that Picture:

After creating the TetraMesh, i also get the error:
[Open3D ERROR] [CreateFromPointCloudAlphaShape] invalid tetra in TetraMesh

The code i use:

alpha = 0.002
print(f"alpha={alpha:.3f}")
tetra_mesh, pt_map = o3d.geometry.TetraMesh.create_from_point_cloud(pcd)
o3d.visualization.draw_geometries([pcd,tetra_mesh], mesh_show_back_face=True)
mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha, tetra_mesh, pt_map)
mesh.compute_vertex_normals()
o3d.visualization.draw_geometries([mesh], mesh_show_back_face=True)

[sank96]

I have the same problem, any updates?

[halmusaibeli]

Same issue with me.

Code I am using:

alpha = 0.03
print(f"alpha={alpha:.3f}")
tetra_mesh, pt_map = o3d.geometry.TetraMesh.create_from_point_cloud(pcd)
o3d.visualization.draw_geometries([pcd,tetra_mesh], mesh_show_back_face=True)
mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha, tetra_mesh, pt_map)
mesh.compute_vertex_normals()
o3d.visualization.draw_geometries([mesh], mesh_show_back_face=True)

Output:

mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha, tetra_mesh, pt_map)
RuntimeError: [Open3D ERROR] [CreateFromPointCloudAlphaShape] invalid tetra in TetraMesh

[BenT00le]

im having the same issue is there any way to identify and remove the zero area triangles or the points that cause them before creating the tetramesh

pcd.points = o3d.utility.Vector3dVector(surface)
o3d.visualization.draw_geometries([pcd])
alpha = 0.03
print(f"alpha={alpha:.3f}")
tetra_mesh, pt_map = o3d.geometry.TetraMesh.create_from_point_cloud(pcd)
o3d.visualization.draw_geometries([tetra_mesh])
m = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha, tetra_mesh, pt_map)
m.compute_vertex_normals()
o3d.visualization.draw_geometries([m], mesh_show_back_face=True)

[colinlaney]

Maybe visualize your tetra mesh and the point cloud. Probably there is a tetra that has a triangle with zero area? The problem is here that results in a 0 and would lead to a div by 0.

So, @griegler, it would be nice to exit the current iteration rather than the entire for loop, and only ignore single tetrahedron rather than the entire mesh.

[runette]

any news on this - I am hitting in this in about 10 out of about 250 point clouds. All i am doing i bring in the point cloud and then

pcd = o3d.geometry.PointCloud()
pcd.points = o3d.utility.Vector3dVector(cluster)
pcd.estimate_normals()
try:
    mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, .3)
except Exception as e:
    print(f"Cluster {array['ClusterID'][0]} error {str(e)}")
    mesh = o3d.geometry.TriangleMesh()
return mesh