package require vtk
package require vtkinteraction

# Quadric definition
vtkQuadric quadric
  quadric SetCoefficients .5 1 .2 0 .1 0 0 .2 0 0

vtkSampleFunction sample
  sample SetSampleDimensions 30 30 30
  sample SetImplicitFunction quadric
  sample ComputeNormalsOff

vtkExtractVOI extract
  extract SetInput [sample GetOutput]
  extract SetVOI 0 29 0 29 15 15
  extract SetSampleRate 1 2 3

vtkContourFilter contours
  contours SetInput [extract GetOutput]
  contours GenerateValues 13 0.0 1.2

vtkPolyDataMapper contMapper
  contMapper SetInput [contours GetOutput]
  contMapper SetScalarRange 0.0 1.2

vtkActor contActor
  contActor SetMapper contMapper

# Create outline
vtkOutlineFilter outline
  outline SetInput [sample GetOutput]

vtkPolyDataMapper outlineMapper
  outlineMapper SetInput [outline GetOutput]

vtkActor outlineActor
  outlineActor SetMapper outlineMapper
  eval [outlineActor GetProperty] SetColor 0 0 0

# create graphics objects
vtkRenderer ren1
vtkRenderWindow renWin
    renWin AddRenderer ren1
vtkRenderWindowInteractor iren
    iren SetRenderWindow renWin

ren1 SetBackground 1 1 1
ren1 AddActor contActor
ren1 AddActor outlineActor

[ren1 GetActiveCamera] Zoom 1.5
iren SetUserMethod {wm deiconify .vtkInteract}
iren Initialize;

#renWin SetFileName MSquares.tcl.ppm
#renWin SaveImageAsPPM

wm withdraw .