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# In this example vtkClipPolyData is used to cut a polygonal model
# of a cow in half. In addition, the open clip is closed by triangulating
# the resulting complex polygons.
package require vtk
package require vtkinteraction
package require vtktesting
# First start by reading a cow model. We also generate surface normals for
# prettier rendering.
vtkBYUReader cow
cow SetGeometryFileName "$VTK_DATA_ROOT/Data/Viewpoint/cow.g"
vtkPolyDataNormals cowNormals
cowNormals SetInputConnection [cow GetOutputPort]
# We clip with an implicit function. Here we use a plane positioned near
# the center of the cow model and oriented at an arbitrary angle.
vtkPlane plane
plane SetOrigin 0.25 0 0
plane SetNormal -1 -1 0
# vtkClipPolyData requires an implicit function to define what it is to
# clip with. Any implicit function, including complex boolean combinations
# can be used. Notice that we can specify the value of the implicit function
# with the SetValue method.
vtkClipPolyData clipper
clipper SetInputConnection [cowNormals GetOutputPort]
clipper SetClipFunction plane
clipper GenerateClipScalarsOn
clipper GenerateClippedOutputOn
clipper SetValue 0.5
vtkPolyDataMapper clipMapper
clipMapper SetInputConnection [clipper GetOutputPort]
clipMapper ScalarVisibilityOff
vtkProperty backProp
eval backProp SetDiffuseColor $tomato
vtkActor clipActor
clipActor SetMapper clipMapper
eval [clipActor GetProperty] SetColor $peacock
clipActor SetBackfaceProperty backProp
# Here we are cutting the cow. Cutting creates lines where the cut function
# intersects the model. (Clipping removes a portion of the model but the
# dimension of the data does not change.)
#
# The reason we are cutting is to generate a closed polygon at the boundary
# of the clipping process. The cutter generates line segments, the stripper
# then puts them together into polylines. We then pull a trick and define
# polygons using the closed line segements that the stripper created.
#
vtkCutter cutEdges; #Generate cut lines
cutEdges SetInputConnection [cowNormals GetOutputPort]
cutEdges SetCutFunction plane
cutEdges GenerateCutScalarsOn
cutEdges SetValue 0 0.5
vtkStripper cutStrips; #Forms loops (closed polylines) from cutter
cutStrips SetInputConnection [cutEdges GetOutputPort]
cutStrips Update
vtkPolyData cutPoly; #This trick defines polygons as polyline loop
cutPoly SetPoints [[cutStrips GetOutput] GetPoints]
cutPoly SetPolys [[cutStrips GetOutput] GetLines]
# Triangle filter is robust enough to ignore the duplicate point at the
# beginning and end of the polygons and triangulate them.
vtkTriangleFilter cutTriangles
cutTriangles SetInputData cutPoly
vtkPolyDataMapper cutMapper
cutMapper SetInputData cutPoly
cutMapper SetInputConnection [cutTriangles GetOutputPort]
vtkActor cutActor
cutActor SetMapper cutMapper
eval [cutActor GetProperty] SetColor $peacock
# The clipped part of the cow is rendered wireframe.
vtkPolyDataMapper restMapper
restMapper SetInputConnection [clipper GetClippedOutputPort]
restMapper ScalarVisibilityOff
vtkActor restActor
restActor SetMapper restMapper
[restActor GetProperty] SetRepresentationToWireframe
# Create graphics stuff
#
vtkRenderer ren1
vtkRenderWindow renWin
renWin AddRenderer ren1
vtkRenderWindowInteractor iren
iren SetRenderWindow renWin
# Add the actors to the renderer, set the background and size
ren1 AddActor clipActor
ren1 AddActor cutActor
ren1 AddActor restActor
ren1 SetBackground 1 1 1
ren1 ResetCamera
[ren1 GetActiveCamera] Azimuth 30
[ren1 GetActiveCamera] Elevation 30
[ren1 GetActiveCamera] Dolly 1.5
ren1 ResetCameraClippingRange
renWin SetSize 300 300
iren Initialize
# render the image
#
iren AddObserver UserEvent {wm deiconify .vtkInteract}
# prevent the tk window from showing up then start the event loop
wm withdraw .
# Lets you move the cut plane back and forth by invoking the proc Cut with
# the appropriate plane value (essentially a distance from the original
# plane.
#
proc Cut {v} {
clipper SetValue $v
cutEdges SetValue 0 $v
cutStrips Update
cutPoly SetPoints [[cutStrips GetOutput] GetPoints]
cutPoly SetPolys [[cutStrips GetOutput] GetLines]
cutMapper Update
renWin Render
}
iren Start
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