CapClip

Description¶

This example shows how to generate a "cap" on a clipped vtkPolyData. After clipping with vtkClipPolyData, it uses a clever ''trick'' to convert polylines into polygons. If a polydata file is provided, it will cap it. Otherwise it caps a clipped sphere.

Warning

The clipping is done with a scalar field provided by vtkPlane and results may depend on the resolution of the input vtkPolyData.

Style

This example collects all of the color definition in the beginning of the example. This makes it easier to make changes to the colors without having to search the code.

Other Languages

See (Cxx), (CSharp)

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code¶

CapClip.py

#!/usr/bin/env python

import os.path

import vtk


def get_program_parameters():
    import argparse
    description = 'Clip polydata using a plane.'
    epilogue = '''
    This is an example using vtkClipPolyData to clip input polydata, if provided, or a sphere otherwise.
    '''
    parser = argparse.ArgumentParser(description=description, epilog=epilogue)
    parser.add_argument('filename', nargs='?', default=None, help='Optional input filename e.g cow.g.')
    args = parser.parse_args()
    return args.filename


def main():
    filePath = get_program_parameters()

    # Define colors
    colors = vtk.vtkNamedColors()
    backgroundColor = colors.GetColor3d("steel_blue")
    boundaryColor = colors.GetColor3d("Banana")
    clipColor = colors.GetColor3d("Tomato")

    if filePath and os.path.isfile(filePath):
        polyData = ReadPolyData(filePath)
        if not polyData:
            polyData = GetSpherePD()
    else:
        polyData = GetSpherePD()

    plane = vtk.vtkPlane()
    plane.SetOrigin(polyData.GetCenter())
    plane.SetNormal(1.0, -1.0, -1.0)

    clipper = vtk.vtkClipPolyData()
    clipper.SetInputData(polyData)
    clipper.SetClipFunction(plane)
    clipper.SetValue(0)
    clipper.Update()

    polyData = clipper.GetOutput()

    clipMapper = vtk.vtkDataSetMapper()
    clipMapper.SetInputData(polyData)

    clipActor = vtk.vtkActor()
    clipActor.SetMapper(clipMapper)
    clipActor.GetProperty().SetDiffuseColor(clipColor)
    clipActor.GetProperty().SetInterpolationToFlat()
    clipActor.GetProperty().EdgeVisibilityOn()

    # Now extract feature edges
    boundaryEdges = vtk.vtkFeatureEdges()
    boundaryEdges.SetInputData(polyData)
    boundaryEdges.BoundaryEdgesOn()
    boundaryEdges.FeatureEdgesOff()
    boundaryEdges.NonManifoldEdgesOff()
    boundaryEdges.ManifoldEdgesOff()

    boundaryStrips = vtk.vtkStripper()
    boundaryStrips.SetInputConnection(boundaryEdges.GetOutputPort())
    boundaryStrips.Update()

    # Change the polylines into polygons
    boundaryPoly = vtk.vtkPolyData()
    boundaryPoly.SetPoints(boundaryStrips.GetOutput().GetPoints())
    boundaryPoly.SetPolys(boundaryStrips.GetOutput().GetLines())

    boundaryMapper = vtk.vtkPolyDataMapper()
    boundaryMapper.SetInputData(boundaryPoly)

    boundaryActor = vtk.vtkActor()
    boundaryActor.SetMapper(boundaryMapper)
    boundaryActor.GetProperty().SetDiffuseColor(boundaryColor)

    # create renderer render window, and interactor
    renderer = vtk.vtkRenderer()
    renderWindow = vtk.vtkRenderWindow()
    renderWindow.AddRenderer(renderer)
    interactor = vtk.vtkRenderWindowInteractor()
    interactor.SetRenderWindow(renderWindow)

    # set background color and size
    renderer.SetBackground(backgroundColor)
    renderWindow.SetSize(640, 480)

    # add our actor to the renderer
    renderer.AddActor(clipActor)
    renderer.AddActor(boundaryActor)

    # Generate an interesting view
    renderer.ResetCamera()
    renderer.GetActiveCamera().Azimuth(30)
    renderer.GetActiveCamera().Elevation(30)
    renderer.GetActiveCamera().Dolly(1.2)
    renderer.ResetCameraClippingRange()

    renderWindow.Render()
    renderWindow.SetWindowName('CapClip')
    renderWindow.Render()

    interactor.Start()


def ReadPolyData(file_name):
    import os
    path, extension = os.path.splitext(file_name)
    extension = extension.lower()
    if extension == ".ply":
        reader = vtk.vtkPLYReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == ".vtp":
        reader = vtk.vtkXMLpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == ".obj":
        reader = vtk.vtkOBJReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == ".stl":
        reader = vtk.vtkSTLReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == ".vtk":
        reader = vtk.vtkpoly_dataReader()
        reader.SetFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    elif extension == ".g":
        reader = vtk.vtkBYUReader()
        reader.SetGeometryFileName(file_name)
        reader.Update()
        poly_data = reader.GetOutput()
    else:
        # Return a None if the extension is unknown.
        poly_data = None
    return poly_data


def GetSpherePD():
    """
    :return: The PolyData representation of a sphere.
    """
    source = vtk.vtkSphereSource()
    source.SetThetaResolution(20)
    source.SetPhiResolution(11)
    source.Update()
    return source.GetOutput()


if __name__ == '__main__':
    main()