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package require vtk
package require vtkinteraction
# Create the RenderWindow and Renderer
vtkRenderer ren1
vtkRenderWindow renWin
renWin AddRenderer ren1
vtkRenderWindowInteractor iren
iren SetRenderWindow renWin
# create a default polygonal sphere
vtkSphereSource sphere
vtkPolyDataMapper sphmapper
sphmapper SetInputConnection [sphere GetOutputPort]
vtkActor sphactor
sphactor SetMapper sphmapper
# Add the actors to the renderer, set the background to initial
# color (which is also transparent), set size.
ren1 AddActor sphactor
ren1 SetBackground 0.1 0.2 0.4
renWin SetSize 256 256
# render first image
renWin Render
# create window to image filter, grabbing RGB and alpha
vtkWindowToImageFilter w2i
w2i SetInput renWin
w2i SetInputBufferTypeToRGBA
# grab window
w2i Update
# set up mappers and actors to display the image
vtkImageMapper im
im SetColorWindow 255
im SetColorLevel 127.5
im SetInputConnection [w2i GetOutputPort]
vtkActor2D ia2
ia2 SetMapper im
# now, change the image (background is now green)
sphactor SetScale 2 2 2
ren1 SetBackground 0 1 0
# add the image of the sphere (keeping the original sphere too)
ren1 AddActor ia2
ren1 SetViewport 0 0 1 1
# render result (the polygonal sphere appears behind a smaller image
# of itself). Background of original image is transparent, so you
# can see through it back to the larger sphere and new background.
renWin Render
iren AddObserver UserEvent {wm deiconify .vtkInteract}
# prevent the tk window from showing up then start the event loop
wm withdraw .
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