# ImplicitPolyDataDistance

VTKExamples/Python/PolyData/ImplicitPolyDataDistance

### Description

Shows how to use vtkImplicitPolyDataDistance.

### Code

ImplicitPolyDataDistance.py

    import vtk
    import numpy as np

    sphereSource = vtk.vtkSphereSource()
    sphereSource.SetCenter(0.0, 0.0, 0.0)
    sphereSource.SetRadius(1.0)
    sphereSource.Update()

    sphereMapper = vtk.vtkPolyDataMapper()
    sphereMapper.SetInputConnection(sphereSource.GetOutputPort())
    sphereMapper.ScalarVisibilityOff()

    sphereActor = vtk.vtkActor()
    sphereActor.SetMapper(sphereMapper)
    sphereActor.GetProperty().SetOpacity(.3)
    sphereActor.GetProperty().SetColor(1, 0, 0)

    implicitPolyDataDistance = vtk.vtkImplicitPolyDataDistance()
    implicitPolyDataDistance.SetInput(sphereSource.GetOutput())

    # Setup a grid
    points = vtk.vtkPoints()
    step = 0.1
    for x in np.arange(-2, 2, step):
        for y in np.arange(-2, 2, step):
            for z in np.arange(-2, 2, step):
                points.InsertNextPoint(x, y, z)

    # Add distances to each point
    signedDistances = vtk.vtkFloatArray()
    signedDistances.SetNumberOfComponents(1)
    signedDistances.SetName("SignedDistances")

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

    polyData = vtk.vtkPolyData()
    polyData.SetPoints(points)
    polyData.GetPointData().SetScalars(signedDistances)

    vertexGlyphFilter = vtk.vtkVertexGlyphFilter()
    vertexGlyphFilter.SetInputData(polyData)
    vertexGlyphFilter.Update()

    signedDistanceMapper = vtk.vtkPolyDataMapper()
    signedDistanceMapper.SetInputConnection(vertexGlyphFilter.GetOutputPort())
    signedDistanceMapper.ScalarVisibilityOn()

    signedDistanceActor = vtk.vtkActor()
    signedDistanceActor.SetMapper(signedDistanceMapper)

    renderer = vtk.vtkRenderer()
    renderer.AddViewProp(sphereActor)
    renderer.AddViewProp(signedDistanceActor)

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

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

    renderWindow.Render()
    renWinInteractor.Start()