# TensorEllipsoids

VTKExamples/Python/VisualizationAlgorithms/TensorEllipsoids

### Description

This example visualizes the analytical results of Boussinesq's problem from Saada. The figure shows the results by displaying the scaled and oriented principal axes as tensor ellipsoids representing the stress tensor. (These are called tensor axes.)

### Code

TensorEllipsoids.py

    #!/usr/bin/env python

    # Translated from TenEllip.tcl

    import vtk

    def main():
        colors = vtk.vtkNamedColors()

        # Create the RenderWindow, Renderer and interactive renderer.
        #
        ren = vtk.vtkRenderer()
        renWin = vtk.vtkRenderWindow()
        renWin.AddRenderer(ren)
        iren = vtk.vtkRenderWindowInteractor()
        iren.SetRenderWindow(renWin)

        # Generate the tensors.
        ptLoad = vtk.vtkPointLoad()
        ptLoad.SetLoadValue(100.0)
        ptLoad.SetSampleDimensions(6, 6, 6)
        ptLoad.ComputeEffectiveStressOn()
        ptLoad.SetModelBounds(-10, 10, -10, 10, -10, 10)

        # Extract a plane of data.
        plane = vtk.vtkImageDataGeometryFilter()
        plane.SetInputConnection(ptLoad.GetOutputPort())
        plane.SetExtent(2, 2, 0, 99, 0, 99)

        # Generate the ellipsoids.
        sphere = vtk.vtkSphereSource()
        sphere.SetThetaResolution(8)
        sphere.SetPhiResolution(8)
        tensorEllipsoids = vtk.vtkTensorGlyph()
        tensorEllipsoids.SetInputConnection(ptLoad.GetOutputPort())
        tensorEllipsoids.SetSourceConnection(sphere.GetOutputPort())
        tensorEllipsoids.SetScaleFactor(10)
        tensorEllipsoids.ClampScalingOn()

        ellipNormals = vtk.vtkPolyDataNormals()
        ellipNormals.SetInputConnection(tensorEllipsoids.GetOutputPort())

        # Map contour
        lut = vtk.vtkLookupTable()
        MakeLogLUT(lut)
        # lut.SetHueRange(.6667, 0.0)
        tensorEllipsoidsMapper = vtk.vtkPolyDataMapper()
        tensorEllipsoidsMapper.SetInputConnection(ellipNormals.GetOutputPort())
        tensorEllipsoidsMapper.SetLookupTable(lut)
        plane.Update()  # force update for scalar range
        tensorEllipsoidsMapper.SetScalarRange(plane.GetOutput().GetScalarRange())

        tensorActor = vtk.vtkActor()
        tensorActor.SetMapper(tensorEllipsoidsMapper)

        # Create an outline around the data.
        #
        outline = vtk.vtkOutlineFilter()
        outline.SetInputConnection(ptLoad.GetOutputPort())

        outlineMapper = vtk.vtkPolyDataMapper()
        outlineMapper.SetInputConnection(outline.GetOutputPort())

        outlineActor = vtk.vtkActor()
        outlineActor.SetMapper(outlineMapper)
        outlineActor.GetProperty().SetColor(colors.GetColor3d("Black"))

        # Create a cone whose apex indicates the application of load.
        #
        coneSrc = vtk.vtkConeSource()
        coneSrc.SetRadius(.5)
        coneSrc.SetHeight(2)
        coneMap = vtk.vtkPolyDataMapper()
        coneMap.SetInputConnection(coneSrc.GetOutputPort())
        coneActor = vtk.vtkActor()
        coneActor.SetMapper(coneMap)
        coneActor.SetPosition(0, 0, 11)
        coneActor.RotateY(90)
        coneActor.GetProperty().SetColor(colors.GetColor3d("Red"))

        camera = vtk.vtkCamera()
        camera.SetFocalPoint(0.113766, -1.13665, -1.01919)
        camera.SetPosition(-29.4886, -63.1488, 26.5807)
        camera.SetViewAngle(24.4617)
        camera.SetViewUp(0.17138, 0.331163, 0.927879)
        camera.SetClippingRange(1, 100)

        ren.AddActor(tensorActor)
        ren.AddActor(outlineActor)
        ren.AddActor(coneActor)
        ren.SetBackground(colors.GetColor3d("WhiteSmoke"))
        ren.SetActiveCamera(camera)

        renWin.SetSize(512, 512)

        iren.Initialize()
        renWin.Render()
        iren.Start()

    def MakeLogLUT(lut):
        # Make the lookup using a Brewer palette.
        colorSeries = vtk.vtkColorSeries()
        colorSeries.SetNumberOfColors(8)
        colorSeriesEnum = colorSeries.BREWER_DIVERGING_SPECTRAL_8
        colorSeries.SetColorScheme(colorSeriesEnum)
        lut.SetScaleToLog10()
        colorSeries.BuildLookupTable(lut, colorSeries.ORDINAL)
        lut.SetNanColor(1, 0, 0, 1)
        # Original
        # lut.SetScaleToLog10()
        # lut.SetHueRange(.6667, 0.0)
        # lut.Build()

    if __name__ == '__main__':
        main()