[vtkusers] Is it possible to render two intersected ImageData as Volume?

[Jordi Campos i Miralles]

Hi,

When I load 2 intersected ImageData files and try to render them as
Volume, the last one is always rendered over the first one.

Is there any way to avoid this behaviour?

I also tried to make and assembly of both volumes before adding them to
the renderer, but I obtain the same result.

I first "detected the problem" in Paraview, but I also tested it in
"plain VTK" with the same behavior.

What am I doing wrong?

Thanks,

jor;)i

Listings:

- 15-VolumesIntersected-2Volumes.py
- 15-VolumesIntersected-Assembly.py



#!/usr/bin/python
#                                        15-VolumesIntersected-2Volumes.py
import vtk
from   vtk     import *

def main():
  alphaTF = vtkPiecewiseFunction()                       # Opacity (A-TF)
  alphaTF.AddPoint(  0.0, 1.0) ; alphaTF.AddPoint( 42.0, 1.0)
  
  colorTF = vtkColorTransferFunction()                   # Color (RGB-TF)
  colorTF.AddRGBPoint(  0, 0, 1, 0) ; colorTF.AddRGBPoint( 42, 1, 0, 0)
  
  volProp = vtkVolumeProperty()                          # VolumeProperty
  volProp.SetColor(colorTF) ; volProp.SetScalarOpacity(alphaTF)
  volProp.SetInterpolationTypeToLinear()
  
  ren = vtkRenderer()                                    # Renderer
  createMapperAndVtkVolume( "teddy-64-body.vti", volProp, ren )
  createMapperAndVtkVolume( "teddy-64-armR.vti", volProp, ren )
  ren.ResetCamera()
  
  renwin = vtkRenderWindow()                             # Window
  renwin.AddRenderer(ren)
  renwin.SetSize(300, 300)
  
  iren = vtkRenderWindowInteractor()                     # Interactor
  iren.SetRenderWindow(renwin)
  iren.Start()
  
def createMapperAndVtkVolume( fileName, volProp, renderer ):
  source  = vtkXMLImageDataReader()                      # Read: Body
  source.SetFileName( fileName )

  volumeMapper = vtkVolumeRayCastMapper()                # Mapper
  cast = vtkImageCast()                                  # - uchar conversion
  cast.SetInput( source.GetOutput() )                      #  (required by VRayCast)
  cast.SetOutputScalarTypeToUnsignedChar()
  volumeMapper.SetInput( cast.GetOutput() )
  compositeFunc = vtkVolumeRayCastCompositeFunction()    # - composite
  volumeMapper.SetVolumeRayCastFunction(compositeFunc)
  
  volume = vtkVolume()                                   # Volume=Mapper+Property
  volume.SetMapper(volumeMapper)
  volume.SetProperty(volProp)
  
  renderer.AddVolume(volume)

main()










#!/usr/bin/python
#                                       15-VolumesIntersected-Assembly.py
import vtk
from   vtk     import *

def main():
  alphaTF = vtkPiecewiseFunction()                       # Opacity (A-TF)
  alphaTF.AddPoint(  0.0, 1.0) ; alphaTF.AddPoint( 42.0, 1.0)
  
  colorTF = vtkColorTransferFunction()                   # Color (RGB-TF)
  colorTF.AddRGBPoint(  0, 0, 1, 0) ; colorTF.AddRGBPoint( 42, 1, 0, 0)
  
  volProp = vtkVolumeProperty()                          # VolumeProperty
  volProp.SetColor(colorTF) ; volProp.SetScalarOpacity(alphaTF)
  volProp.SetInterpolationTypeToLinear()
  
  ren      = vtkRenderer()                               # Renderer
  assembly = vtk.vtkAssembly()                           # Assembly

  createMapperAndVtkVolume( "teddy-64-body.vti", volProp, assembly )
  createMapperAndVtkVolume( "teddy-64-armR.vti", volProp, assembly )

  ren.AddVolume( assembly )
  ren.ResetCamera()
  
  renwin = vtkRenderWindow()                             # Window
  renwin.AddRenderer(ren)
  renwin.SetSize(300, 300)
  
  iren = vtkRenderWindowInteractor()                     # Interactor
  iren.SetRenderWindow(renwin)
  iren.Start()
  
def createMapperAndVtkVolume( fileName, volProp, assembly ):
  source  = vtkXMLImageDataReader()                      # Read: Body
  source.SetFileName( fileName )

  volumeMapper = vtkVolumeRayCastMapper()                # Mapper
  cast = vtkImageCast()                                  # - uchar conversion
  cast.SetInput( source.GetOutput() )                      #  (required by VRayCast)
  cast.SetOutputScalarTypeToUnsignedChar()
  volumeMapper.SetInput( cast.GetOutput() )
  compositeFunc = vtkVolumeRayCastCompositeFunction()    # - composite
  volumeMapper.SetVolumeRayCastFunction(compositeFunc)
  
  volume = vtkVolume()                                   # Volume=Mapper+Property
  volume.SetMapper(volumeMapper)
  volume.SetProperty(volProp)
  
  assembly.AddPart( volume )

main()



-- 
Jordi Campos i Miralles
Departament de Matemàtica Aplicada i Anàlisi, MAiA
Facultat de Matemàtiques, Universitat de Barcelona
Gran Via de les Corts Catalanes, 585
08007 Barcelona
Telf : +34 93 403 93 72