[vtk-developers] How to extract a part defined by closed points inside a unstructured Grid Surface

[darkcminor]

I want to extract a part of a surface  defined here by red points, in fact it
is a closed contour (What I want is to get a piece of cake defined by
contour)

I have this:

<http://vtk.1045678.n5.nabble.com/file/n5726086/have.png> 


To get taht The current code is


/package require vtk

# Create a reader to read the unstructured grid data. We use a 
# vtkDataSetReader which means the type of the output is unknown until
# the data file is read.  
vtkDEMReader reader
    reader SetFileName "$VTK_DATA_ROOT/Data/SainteHelens.dem"
    reader Update
    puts "Dataset reader actual memory: [[reader GetOutput]
GetActualMemorySize]"
    puts "Dataset reader no of points: [[reader GetOutput]
GetNumberOfPoints]"

set lo [lindex [[reader GetOutput] GetScalarRange] 0]
set hi [lindex [[reader GetOutput] GetScalarRange] 1]

# Get the physical xy extent of dataset
scan [[reader GetOutput] GetWholeExtent] "%d %d %d %d %d %d" XminR XmaxR
YminR YmaxR ZminR ZmaxR
puts "Physical extent of dataset: $XminR $XmaxR $YminR $YmaxR $ZminR $ZmaxR"

# trims off points with no data (value -9999) in DEMS converted
# from ASCII arc grid files. This step could be used to crop the data
# at another elevation by changing the threshold value
vtkThreshold cropped
  cropped SetInput [reader GetOutput]
  cropped ThresholdByUpper -9998; # threshold value
  cropped Update
  puts "Threshold filter no of cells : [[cropped GetOutput]
GetNumberOfCells]"
  puts "Threshold filter no of points: [[cropped GetOutput]
GetNumberOfPoints]" 

# Create the geometry conneting the grid of location points
# at this point the surface is flat with an x-y grid of numbers 
# (scalars) representing elevations
vtkGeometryFilter geom
  geom SetInput [cropped GetOutput]
  geom Update
  puts "Geometry filter no of cells : [[geom GetOutput] GetNumberOfCells]"
  puts "Geometry filter no of points: [[geom GetOutput] GetNumberOfPoints]"

# Now warp the surface based on the scalar elevation values
# This creates the 3D mesh model of the terrain.
vtkWarpScalar surface
  surface SetInput [geom GetOutput]
  surface SetScaleFactor 1; # $scale variable controls vertical exaggeration
  surface Update
  #surface UseNormalOn
  #surface SetNormal 0 0 1
  puts "Warp scalar no of cells : [[surface GetOutput] GetNumberOfCells]"
  puts "Warp scalar no of points: [[surface GetOutput] GetNumberOfPoints]"



# Map dataset to graphics primitives
#
vtkDataSetMapper demMapper
  demMapper SetInputConnection [surface GetOutputPort]
  demMapper ScalarVisibilityOff; # This prevents surface being colored based
on scalar value

#
===========================================================================
# Create actor for surface topogrpahy
#
===========================================================================

vtkLODActor demActor
  demActor SetMapper demMapper
  [demActor GetProperty] SetInterpolationToGouraud
  [demActor GetProperty] SetRepresentationToSurface

#
===========================================================================
# Create projected terrain path
#
===========================================================================

# Create some paths
vtkPoints pts
  pts InsertNextPoint 562669 5.1198e+006 1992.77
  pts InsertNextPoint 562100 5.1170e+006 1900.77
  pts InsertNextPoint 562850 5.11181e+006 1912.57
  pts InsertNextPoint 562659 5.1198e+006 1992.77
  
  
  
vtkCellArray lines
  lines InsertNextCell 4
  lines InsertCellPoint 0
  lines InsertCellPoint 1
  lines InsertCellPoint 2
  lines InsertCellPoint 3  

vtkPolyData terrainPaths
  terrainPaths SetPoints pts
  terrainPaths SetLines lines

vtkProjectedTerrainPath projectedPaths
  projectedPaths SetInput terrainPaths
  projectedPaths SetSource [reader GetOutput]
  projectedPaths SetHeightOffset 25
  projectedPaths SetHeightTolerance 5
  projectedPaths SetProjectionModeToNonOccluded
  projectedPaths SetProjectionModeToHug
  projectedPaths Update
  puts "Projected path filter no of cells : [[projectedPaths GetOutput]
GetNumberOfCells]"

#vtkPolyDataMapper pathMapper
#  pathMapper SetInputConnection [projectedPaths GetOutputPort]

vtkTubeFilter pathTube
  pathTube SetNumberOfSides 8
  pathTube SetInputConnection [projectedPaths GetOutputPort]
  pathTube SetRadius 10

vtkPolyDataMapper pathTubeMapper
  pathTubeMapper SetInputConnection [pathTube GetOutputPort]

vtkActor pathActor
  pathActor SetMapper pathTubeMapper
  [pathActor GetProperty] SetColor 1 0 0
  [pathActor GetProperty] SetSpecular .3
  [pathActor GetProperty] SetSpecularPower 30

#
===========================================================================
# Create a cell picker
#
===========================================================================

# Create a cell picker.
vtkCellPicker picker
    picker AddObserver EndPickEvent annotatePick

# Create a text mapper and actor to display the results of picking.
vtkTextMapper textMapper
set tprop [textMapper GetTextProperty]
    $tprop SetFontFamilyToArial
    $tprop SetFontSize 10
    $tprop BoldOn
    $tprop ShadowOn
    $tprop SetColor 1 0 0
vtkActor2D textActor
    textActor VisibilityOff
    textActor SetMapper textMapper

#
===========================================================================
# Create renderer, render window and add actors to the renderer
#
===========================================================================

# Create the RenderWindow, Renderer and both Actors
#
vtkRenderer ren1
vtkRenderWindow renWin
  renWin AddRenderer ren1
vtkRenderWindowInteractor iren
  iren SetRenderWindow renWin
  iren SetPicker picker

# Add the actors to the renderer, set the background and size
#
  ren1 AddActor demActor
  ren1 AddActor pathActor
  ren1 AddActor2D textActor
  #ren1 AddActor probeActor
  ren1 SetBackground .1 .2 .4

  iren AddObserver UserEvent {wm deiconify .vtkInteract}
  iren SetDesiredUpdateRate 5

  ren1 ResetCamera
  ren1 ResetCameraClippingRange

  renWin Render

wm withdraw .

# Create a Tcl procedure to create the text for the text mapper used to
# display the results of picking.
proc annotatePick {} {
    if { [picker GetCellId] < 0 } {
	textActor VisibilityOff

    } else {
	set selPt [picker GetSelectionPoint]
	set x [lindex $selPt 0] 
	set y [lindex $selPt 1]
	set pickPos [picker GetPickPosition]
	set xp [lindex $pickPos 0] 
	set yp [lindex $pickPos 1]
	set zp [lindex $pickPos 2]

	textMapper SetInput "($xp, $yp, $zp)"
	textActor SetPosition $x $y
	textActor VisibilityOn
    }

    renWin Render
}/

Now I was taking a look at vtkExtractGrid, however as surface is no
structured grid I do not know how to extract a part of the surface, 
I was trying

/vtkExtractGrid extract
  extract SetVOI 1 55 -1000 1000 -1000 1000
  extract SetInputData #pass reader Output as surface?

vtkPlane plane
  plane SetOrigin 0 4 2
  plane SetNormal 0 1 0
vtkCutter cutter
  cutter SetInputConnection [extract GetOutputPort]
  cutter SetCutFunction plane
  cutter GenerateCutScalarsOff
  cutter SetSortByToSortByCell

vtkLookupTable clut
  clut SetHueRange 0 .67
  clut Build

vtkPolyDataMapper cutterMapper
cutterMapper SetInputConnection [cutter GetOutputPort]
cutterMapper SetScalarRange .18 .7
cutterMapper SetLookupTable clut

vtkActor cut
  cut SetMapper cutterMapper
/

Could you please suggest an idea on how to extract or cut this surface
defined by contour?



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