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Tutorial Step6

vtk-examples/Python/Tutorial/Tutorial_Step6


Description

This example introduces 3D widgets. 3D widgets take advantage of the event/observer design pattern introduced previously. They typically have a particular representation in the scene which can be interactively selected and manipulated using the mouse and keyboard. As the widgets are manipulated, they in turn invoke events such as StartInteractionEvent, InteractionEvent, and EndInteractionEvent which can be used to manipulate the scene that the widget is embedded in. 3D widgets work in the context of the event loop which was set up in the previous example.

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Question

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Code

Tutorial_Step6.py

#!/usr/bin/env python

"""
=========================================================================

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/

"""

# First access the VTK module (and any other needed modules) by importing them.
import vtk


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

    #
    # Next we create an instance of vtkConeSource and set some of its
    # properties. The instance of vtkConeSource 'cone' is part of a
    # visualization pipeline (it is a source process object) it produces data
    # (output type is vtkPolyData) which other filters may process.
    #
    cone = vtk.vtkConeSource()
    cone.SetHeight(3.0)
    cone.SetRadius(1.0)
    cone.SetResolution(10)

    #
    # In this example we terminate the pipeline with a mapper process object.
    # (Intermediate filters such as vtkShrinkPolyData could be inserted in
    # between the source and the mapper.)  We create an instance of
    # vtkPolyDataMapper to map the polygonal data into graphics primitives. We
    # connect the output of the cone source to the input of this mapper.
    #
    coneMapper = vtk.vtkPolyDataMapper()
    coneMapper.SetInputConnection(cone.GetOutputPort())

    #
    # Create an actor to represent the cone. The actor orchestrates rendering
    # of the mapper's graphics primitives. An actor also refers to properties
    # via a vtkProperty instance, and includes an internal transformation
    # matrix. We set this actor's mapper to be coneMapper which we created
    # above.
    #
    coneActor = vtk.vtkActor()
    coneActor.SetMapper(coneMapper)
    coneActor.GetProperty().SetColor(colors.GetColor3d('Bisque'))

    #
    # Create the Renderer and assign actors to it. A renderer is like a
    # viewport. It is part or all of a window on the screen and it is
    # responsible for drawing the actors it has.  We also set the background
    # color here.
    #
    ren1 = vtk.vtkRenderer()
    ren1.AddActor(coneActor)
    ren1.SetBackground(colors.GetColor3d('MidnightBlue'))

    #
    # Finally we create the render window which will show up on the screen.
    # We put our renderer into the render window using AddRenderer. We also
    # set the size to be 300 pixels by 300.
    #
    renWin = vtk.vtkRenderWindow()
    renWin.AddRenderer(ren1)
    renWin.SetSize(300, 300)
    renWin.SetWindowName('Tutorial_Step6')

    #
    # The vtkRenderWindowInteractor class watches for events (e.g., keypress,
    # mouse) in the vtkRenderWindow. These events are translated into
    # event invocations that VTK understands (see VTK/Common/vtkCommand.h
    # for all events that VTK processes). Then observers of these VTK
    # events can process them as appropriate.
    iren = vtk.vtkRenderWindowInteractor()
    iren.SetRenderWindow(renWin)

    #
    # By default the vtkRenderWindowInteractor instantiates an instance
    # of vtkInteractorStyle. vtkInteractorStyle translates a set of events
    # it observes into operations on the camera, actors, and/or properties
    # in the vtkRenderWindow associated with the vtkRenderWinodwInteractor.
    # Here we specify a particular interactor style.
    style = vtk.vtkInteractorStyleTrackballCamera()
    iren.SetInteractorStyle(style)

    #
    # Here we use a vtkBoxWidget to transform the underlying coneActor (by
    # manipulating its transformation matrix). Many other types of widgets
    # are available for use, see the documentation for more details.
    #
    # The SetInteractor method is how 3D widgets are associated with the render
    # window interactor. Internally, SetInteractor sets up a bunch of callbacks
    # using the Command/Observer mechanism (AddObserver()). The place factor
    # controls the initial size of the widget with respect to the bounding box
    # of the input to the widget.
    boxWidget = vtk.vtkBoxWidget()
    boxWidget.SetInteractor(iren)
    boxWidget.SetPlaceFactor(1.25)
    boxWidget.GetOutlineProperty().SetColor(colors.GetColor3d('Gold'))

    #
    # Place the interactor initially. The input to a 3D widget is used to
    # initially position and scale the widget. The EndInteractionEvent is
    # observed which invokes the SelectPolygons callback.
    #
    boxWidget.SetProp3D(coneActor)
    boxWidget.PlaceWidget()
    callback = vtkMyCallback()
    boxWidget.AddObserver('InteractionEvent', callback)

    #
    # Normally the user presses the 'i' key to bring a 3D widget to life. Here
    # we will manually enable it so it appears with the cone.
    #
    boxWidget.On()

    #
    # Start the event loop.
    #
    iren.Initialize()
    iren.Start()


class vtkMyCallback(object):
    """
    Callback for the interaction.
    """

    def __call__(self, caller, ev):
        t = vtk.vtkTransform()
        widget = caller
        widget.GetTransform(t)
        widget.GetProp3D().SetUserTransform(t)


if __name__ == '__main__':
    import sys

    main(sys.argv)