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# TextOrigin

VTKEx/Python/Annotation/TextOrigin

This example demonstrates the use of vtkVectorText and vtkFollower. vtkVectorText is used to create 3D annotation. vtkFollower is used to position the 3D text and to ensure that the text always faces the renderer's active camera (i.e., the text is always readable).

Other languages

See (Cxx), (Java)

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### Code

TextOrigin.py

    #!/usr/bin/env python

    import vtk

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

        # Create the axes and the associated mapper and actor.
        axes = vtk.vtkAxes()
        axes.SetOrigin(0, 0, 0)
        axesMapper = vtk.vtkPolyDataMapper()
        axesMapper.SetInputConnection(axes.GetOutputPort())
        axesActor = vtk.vtkActor()
        axesActor.SetMapper(axesMapper)

        # Create the 3D text and the associated mapper and follower (a type of actor).  Position the text so it is displayed over the origin of the axes.
        atext = vtk.vtkVectorText()
        atext.SetText("Origin")
        textMapper = vtk.vtkPolyDataMapper()
        textMapper.SetInputConnection(atext.GetOutputPort())
        textActor = vtk.vtkFollower()
        textActor.SetMapper(textMapper)
        textActor.SetScale(0.2, 0.2, 0.2)
        textActor.AddPosition(0, -0.1, 0)

        # Create the Renderer, RenderWindow, and RenderWindowInteractor.
        renderer = vtk.vtkRenderer()
        renderWindow = vtk.vtkRenderWindow()
        renderWindow.AddRenderer(renderer)
        renderWindow.SetSize(640, 480)

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

        style = vtk.vtkInteractorStyleTrackballCamera()
        interactor.SetInteractorStyle(style)

        # Add the actors to the renderer.
        renderer.AddActor(axesActor)
        renderer.AddActor(textActor)

        renderer.SetBackground(colors.GetColor3d("Silver"))

        # Zoom in closer.
        renderer.ResetCamera()
        renderer.GetActiveCamera().Zoom(1.6)

        renderer.SetBackground(colors.GetColor3d("Silver"))

        # Reset the clipping range of the camera; set the camera of the follower; render.
        renderer.ResetCameraClippingRange()
        textActor.SetCamera(renderer.GetActiveCamera())

        interactor.Initialize()
        renderWindow.Render()
        interactor.Start()

    if __name__ == '__main__':
        main()