# ClipDataSetWithPolydata

VTKExamples/Python/Meshes/ClipDataSetWithPolydata

### Description

An example that shows how to use the vtkClipDataSet to clip a vtkRectilinearGrid with an arbitrary polydata. vtkImplicitPolyDataDistance is used to turn the polydata into an implicit function. Every point of the grid is evaluated before sending to vtkClipDataSet. This example uses a vtkConeSource to generate polydata to use, however any polydata could be used, including stl files.

### Code

ClipDataSetWithPolydata.py

    import vtk
    import numpy as np

    # Create polydata to slice the grid with. In this case, use a cone. This could
    # be any polydata including a stl file.
    cone = vtk.vtkConeSource()
    cone.SetResolution(20)
    cone.Update()

    # implicit function that will be used to slice the mesh
    implicitPolyDataDistance = vtk.vtkImplicitPolyDataDistance()
    implicitPolyDataDistance.SetInput(cone.GetOutput())

    # create a grid
    xCoords = vtk.vtkFloatArray()
    for x, i in enumerate(np.linspace(-1.0, 1.0, 15)):
        xCoords.InsertNextValue(i)

    yCoords = vtk.vtkFloatArray()
    for y, i in enumerate(np.linspace(-1.0, 1.0, 15)):
        yCoords.InsertNextValue(i)

    zCoords = vtk.vtkFloatArray()
    for z, i in enumerate(np.linspace(-1.0, 1.0, 15)):
        zCoords.InsertNextValue(i)

    # The coordinates are assigned to the rectilinear grid. Make sure that
    # the number of values in each of the XCoordinates, YCoordinates,
    # and ZCoordinates is equal to what is defined in SetDimensions().
    rgrid = vtk.vtkRectilinearGrid()
    rgrid.SetDimensions(x+1, y+1, z+1)
    rgrid.SetXCoordinates(xCoords)
    rgrid.SetYCoordinates(yCoords)
    rgrid.SetZCoordinates(zCoords)

    # Create an array to hold distance information
    signedDistances = vtk.vtkFloatArray()
    signedDistances.SetNumberOfComponents(1)
    signedDistances.SetName("SignedDistances")

    # Evaluate the signed distance function at all of the grid points
    for pointId in range(rgrid.GetNumberOfPoints()):
        p = rgrid.GetPoint(pointId)
        signedDistance = implicitPolyDataDistance.EvaluateFunction(p)
        signedDistances.InsertNextValue(signedDistance)

    # add the SignedDistances to the grid
    rgrid.GetPointData().SetScalars(signedDistances)

    # use vtkClipDataSet to slice the grid with the polydata
    clipper = vtk.vtkClipDataSet()
    clipper.SetInputData(rgrid)
    clipper.InsideOutOn()
    clipper.SetValue(0.0)
    clipper.Update()

    # --- mappers, actors, render, etc. ---
    # mapper and actor to view the cone
    coneMapper = vtk.vtkPolyDataMapper()
    coneMapper.SetInputConnection(cone.GetOutputPort())
    coneActor = vtk.vtkActor()
    coneActor.SetMapper(coneMapper)

    # geometry filter to view the background grid
    geometryFilter = vtk.vtkRectilinearGridGeometryFilter()
    geometryFilter.SetInputData(rgrid)
    geometryFilter.SetExtent(0, x+1, 0, y+1, (z+1)//2, (z+1)//2)
    geometryFilter.Update()

    rgridMapper = vtk.vtkPolyDataMapper()
    rgridMapper.SetInputConnection(geometryFilter.GetOutputPort())

    wireActor = vtk.vtkActor()
    wireActor.SetMapper(rgridMapper)
    wireActor.GetProperty().SetRepresentationToWireframe()
    wireActor.GetProperty().SetColor(.1, .1, .1)

    # mapper and actor to view the clipped mesh
    clipperMapper = vtk.vtkDataSetMapper()
    clipperMapper.SetInputConnection(clipper.GetOutputPort())

    clipperActor = vtk.vtkActor()
    clipperActor.SetMapper(clipperMapper)
    clipperActor.GetProperty().SetRepresentationToWireframe()
    clipperActor.GetProperty().SetColor(.1, .1, .1)

    # A renderer and render window
    renderer = vtk.vtkRenderer()
    renderer.SetBackground(1, 1, 1)

    # add the actors
    #renderer.AddActor(coneActor)
    renderer.AddActor(wireActor)
    renderer.AddActor(clipperActor)

    renwin = vtk.vtkRenderWindow()
    renwin.AddRenderer(renderer)

    # An interactor
    interactor = vtk.vtkRenderWindowInteractor()
    interactor.SetRenderWindow(renwin)

    # Start
    interactor.Initialize()
    interactor.Start()