# AnimateVectors

VTKExamples/Python/Texture/AnimateVectors

### Description

Texture maps can be animated as a function of time. By choosing a texture map whose intensity varies monotonically from dark to light, and then “moving” the texture along an object,the object appears to crawl in the direction of the texture map motion. We can use this technique to add apparent motion to things like hedgehogs to show vector magnitude. This example uses texture map animation to simulate vector field motion.

Cite

See B. Yamrom and K. M. Martin. Vector Field Animation with Texture Maps. IEEE Computer Graphics and Applications. 15(2):22–24, 1995 for background.

### Code

AnimateVectors.py

    #!/usr/bin/env python

    import vtk

    def main():
        fileNames = [""] * 2
        fileNames[0], fileNames[1] = get_program_parameters()

        # Generate the other vecAnim file names. There are 8 of them.
        tmpFn = fileNames[1][:-5]
        for i in range(2, 9):
            fileNames.append(tmpFn + str(i) + ".vtk")

        colors = vtk.vtkNamedColors()

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

        # Read the data.
        #
        # Create the pipeline.
        #
        reader = vtk.vtkStructuredPointsReader()
        reader.SetFileName(fileNames[0])

        threshold = vtk.vtkThresholdPoints()
        threshold.SetInputConnection(reader.GetOutputPort())
        threshold.ThresholdByUpper(200)

        line = vtk.vtkLineSource()
        line.SetResolution(1)

        lines = vtk.vtkGlyph3D()
        lines.SetInputConnection(threshold.GetOutputPort())
        lines.SetSourceConnection(line.GetOutputPort())
        lines.SetScaleFactor(0.005)
        lines.SetScaleModeToScaleByScalar()
        lines.Update()

        vectorMapper = vtk.vtkPolyDataMapper()
        vectorMapper.SetInputConnection(lines.GetOutputPort())
        vectorMapper.SetScalarRange(lines.GetOutput().GetScalarRange())

        vectorActor = vtk.vtkActor()
        vectorActor.SetMapper(vectorMapper)
        vectorActor.GetProperty().SetOpacity(0.99)
        vectorActor.GetProperty().SetLineWidth(1.5)

        # Outline
        outline = vtk.vtkOutlineFilter()
        outline.SetInputConnection(reader.GetOutputPort())

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

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

        #  Texture maps.
        textureMaps = list()
        for i in range(2, len(fileNames)):
            tmap = vtk.vtkStructuredPointsReader()
            tmap.SetFileName(fileNames[i])

            texture = vtk.vtkTexture()
            texture.SetInputConnection(tmap.GetOutputPort())
            texture.InterpolateOff()
            texture.RepeatOff()
            textureMaps.append(texture)

        vectorActor.SetTexture(textureMaps[0])

        # Add the actors to the renderer, set the background and size.
        #
        renderer.AddActor(vectorActor)
        renderer.AddActor(outlineActor)

        cam1 = vtk.vtkCamera()
        cam1.SetClippingRange(17.4043, 870.216)
        cam1.SetFocalPoint(136.71, 104.025, 23)
        cam1.SetPosition(204.747, 258.939, 63.7925)
        cam1.SetViewUp(-0.102647, -0.210897, 0.972104)
        cam1.Zoom(1.5)
        renderer.SetActiveCamera(cam1)

        renderer.SetBackground(colors.GetColor3d("Wheat"))
        renderWindow.SetSize(640, 480)

        # Go into a loop.
        for j in range(0, 100):
            for i in range(0, len(textureMaps)):
                vectorActor.SetTexture(textureMaps[i])
                renderWindow.Render()
        interactor.Start()

    def get_program_parameters():
        import argparse
        description = 'Texture maps can be animated as a function of time.'
        epilogue = '''
        This example uses texture map animation to simulate vector field motion.
        '''
        parser = argparse.ArgumentParser(description=description, epilog=epilogue,
                                         formatter_class=argparse.RawDescriptionHelpFormatter)
        parser.add_argument('filename1', help='carotid.vtk.')
        parser.add_argument('filename2', help='vecAnim1.vtk.')
        args = parser.parse_args()
        return args.filename1, args.filename2

    if __name__ == '__main__':
        main()