how to make an open stl file watertight

Newbie here!

I have an STL file which is not watertight and the gap is quite big to repair with the close vertex of the trimesh.

I tried with open3d by following this but I have the following error: "ValueError: vector too long"..

Is there any way to make the mesh watertight? I need to calculate the CoM and Inertia matrix but the values would not be correct if my mesh is not watertight/a closed surface.

For the open3d, firstly I uploaded the stl file, I converted it to numpy and then I used the following code:

        pcd = o3d.geometry.PointCloud()
        pcd.points = o3d.utility.Vector3dVector(DataNP)
        o3d.io.write_point_cloud("testinggggg.ply", pcd)
        poisson_mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_poisson(pcd, depth=8, width=0, scale=1.1, linear_fit=False)[0]
        bbox = pcd.get_axis_aligned_bounding_box()
        p_mesh_crop = poisson_mesh.crop(bbox)
        o3d.io.write_triangle_mesh("output_testinggggg.ply", dec_mesh)

Any help is highly appreciated!

Solution

I have managed to make the mesh watertight. I will post here in case anyone is having troubles in the future with it.

My mesh was actually made of 2 smaller meshes, so I had to first merge them together and then use the VTK library to clean the mesh and fill the holes. This made my mesh watertight and I could calculate everything I needed.

This is the code:

input1 = vtk.vtkPolyData()
input2 = vtk.vtkPolyData()


input1.DeepCopy(Data1.GetOutput())
input2.DeepCopy(Data2.GetOutput())

# Append the two meshes 
appendFilter = vtk.vtkAppendPolyData()

appendFilter.AddInputData(input1)
appendFilter.AddInputData(input2)

appendFilter.Update()

#  Remove any duplicate points.
cleanFilter = vtk.vtkCleanPolyData()
cleanFilter.SetInputConnection(appendFilter.GetOutputPort())
cleanFilter.Update()


# newData = cleanFilter

fill = vtk.vtkFillHolesFilter()
fill.SetInputConnection(appendFilter.GetOutputPort())   
fill.SetHoleSize(100)    
fill.Update()