separate_holes.py

import sys

import vtk


def getInlet_and_Outlets(mesh):
    fillHoles = vtk.vtkFillHolesFilter()
    fillHoles.SetInputData(mesh)
    fillHoles.SetHoleSize(1000.0)
    fillHoles.Update()

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

    # How many added cells
    numOriginalCells = mesh.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()

    conn = vtk.vtkPolyDataConnectivityFilter()
    conn.SetInputData(holePolyData)
    conn.SetExtractionModeToAllRegions()
    conn.Update()

    nregions = conn.GetNumberOfExtractedRegions()

    conn.SetExtractionModeToSpecifiedRegions()
    conn.Update()

    for region in range(nregions):
        print(region)
        conn.InitializeSpecifiedRegionList()
        conn.AddSpecifiedRegion(region)
        conn.Update()

        p = vtk.vtkPolyData()
        p.DeepCopy(conn.GetOutput())

        writer = vtk.vtkSTLWriter()
        writer.SetInputData(p)
        writer.SetFileName(f"saida_{region:02}.stl")
        writer.Write()


if __name__ == "__main__":
    reader = vtk.vtkSTLReader()
    reader.SetFileName(sys.argv[1])
    reader.Update()

    getInlet_and_Outlets(reader.GetOutput())