Python version of CXX IdentifyHoles (https://kitware.github.io/vtk-examples/site/Cxx/Meshes/IdentifyHoles/)

id_holes.py

import sys

import vtk

colors = vtk.vtkNamedColors()

reader = vtk.vtkSTLReader()
reader.SetFileName(sys.argv[1])
reader.Update()

# Fill Holes
fillHoles = vtk.vtkFillHolesFilter()
fillHoles.SetInputConnection(reader.GetOutputPort())
fillHoles.SetHoleSize(1000.0)


# Make the triangle winding order consistent
normals = vtk.vtkPolyDataNormals()
normals.SetInputConnection(fillHoles.GetOutputPort())
normals.ConsistencyOn()
normals.SplittingOff()
normals.Update()
normals.GetOutput().GetPointData().SetNormals(
    reader.GetOutput().GetPointData().GetNormals()
)

# How many added cells
numOriginalCells = reader.GetOutput().GetNumberOfCells()
numNewCells = normals.GetOutput().GetNumberOfCells()

numCells = 0
it = normals.GetOutput().NewCellIterator()
while not it.IsDoneWithTraversal() and numCells < numOriginalCells:
    it.GoToNextCell()
    numCells += 1

print(
    f"Num original: {numOriginalCells}\nNum new: {numNewCells}\nNum added {numNewCells - numOriginalCells}"
)

holePolyData = vtk.vtkPolyData()
holePolyData.Allocate(normals.GetOutput(), numNewCells - numOriginalCells)
holePolyData.SetPoints(normals.GetOutput().GetPoints())

cell = vtk.vtkGenericCell()
# The remaining cells are the new ones from the hole filler
while not it.IsDoneWithTraversal():
    it.GetCell(cell)
    holePolyData.InsertNextCell(it.GetCellType(), cell.GetPointIds())
    it.GoToNextCell()

# We have to use ConnectivtyFilter and not
# PolyDataConnectivityFilter since the later does not create
# RegionIds cell data.
connectivity = vtk.vtkConnectivityFilter()
connectivity.SetInputData(holePolyData)
connectivity.SetExtractionModeToAllRegions()
connectivity.ColorRegionsOn()
connectivity.Update()
print(f"Found {connectivity.GetNumberOfExtractedRegions()} holes")


# Visualize

# Create a mapper and actor for the fill polydata
filledMapper = vtk.vtkDataSetMapper()
filledMapper.SetInputConnection(connectivity.GetOutputPort())
filledMapper.SetScalarModeToUseCellData()
filledMapper.SetScalarRange(
    connectivity.GetOutput().GetCellData().GetArray("RegionId").GetRange()
)
filledActor = vtk.vtkActor()
filledActor.SetMapper(filledMapper)
filledActor.GetProperty().SetDiffuseColor(list(colors.GetColor3d("Peacock")))

# Create a mapper and actor for the original polydata
originalMapper = vtk.vtkPolyDataMapper()
originalMapper.SetInputConnection(reader.GetOutputPort())

backfaceProp = vtk.vtkProperty()
backfaceProp.SetDiffuseColor(list(colors.GetColor3d("Banana")))

originalActor = vtk.vtkActor()
originalActor.SetMapper(originalMapper)
originalActor.SetBackfaceProperty(backfaceProp)
originalActor.GetProperty().SetDiffuseColor(list(colors.GetColor3d("Flesh")))
originalActor.GetProperty().SetRepresentationToWireframe()

# Create a renderer, render window, and interactor
renderer = vtk.vtkRenderer()

renderWindow = vtk.vtkRenderWindow()
renderWindow.SetSize(512, 512)
renderWindow.AddRenderer(renderer)
renderWindow.SetWindowName("IdentifyHoles")

renderWindowInteractor = vtk.vtkRenderWindowInteractor()
renderWindowInteractor.SetRenderWindow(renderWindow)

# Add the actor to the scene
renderer.AddActor(originalActor)
renderer.AddActor(filledActor)
renderer.SetBackground(list(colors.GetColor3d("Burlywood")))

renderer.GetActiveCamera().SetPosition(0, -1, 0)
renderer.GetActiveCamera().SetFocalPoint(0, 0, 0)
renderer.GetActiveCamera().SetViewUp(0, 0, 1)
renderer.GetActiveCamera().Azimuth(60)
renderer.GetActiveCamera().Elevation(30)

renderer.ResetCamera()
# Render and interact
renderWindow.Render()

renderWindowInteractor.Start()