[vtkusers] vtkExtractVOI and volume raycast

Wed Dec 21 13:22:39 EST 2005

I get a white screen and this:

ERROR: In /build/bottoms/vtk-4.4.2/Rendering/vtkVolumeRayCastMapper.cxx, 
line 325
vtkOpenGLVolumeRayCastMapper (0x825cb18): Cannot volume render data of 
type double, only unsigned char or unsigned short.

key pressed
new extent: [-1, -1, -1, -1, -1, -1]

Richard Layman wrote:
> 
> Can someone run the code and confirm the result for linux?
> 
> Thanks.
> 
>> From: "Richard Layman" <mdl_126 at hotmail.com>
>> To: vtkusers at vtk.org
>> Subject: [vtkusers] vtkExtractVOI and volume raycast
>> Date: Tue, 20 Dec 2005 14:01:37 -0500
>>
>> Hope I get responses this time.  Sorry for no subject. I am also 
>> attaching the screen shot for the two cases.
>>
>>> From: "Richard Layman" <mdl_126 at hotmail.com>
>>> To: vtkusers at vtk.org
>>> Subject: [vtkusers] (no subject)
>>> Date: Mon, 19 Dec 2005 14:38:04 -0500
>>>
>>> Hi everyone,
>>>
>>> I made some changes to the VolumeRendering/SimpleRayCast example. 
>>> Basically what I wanted to do is to dynamically select a subvolume 
>>> within a given data volume to render. I use vtkExtractVOI to get the 
>>> subvolume I want and feed this to the rendering pipeline. An outline 
>>> is added for reference.
>>>
>>> As program starts it displays the whole extent. At the press of a 
>>> key, the vtkExtractVOI is given a new extent. And I was hoping to see 
>>> the rendering of the subvolume. This indeed works on Windows. However 
>>> on my Linux system the raycast rendering was shifted relative to the 
>>> new outline.
>>>
>>> My modified code is shown below. Could anyone tell me if this is the 
>>> right way to do this or what I need to do to make it work? I am using 
>>> vtk 4.2 if it's relevant.
>>>
>>> Thanks.
>>>
>>>
>>> #!/usr/bin/env python
>>>
>>> # This is a simple volume rendering example that uses a
>>> # vtkVolumeRayCast mapper
>>>
>>> import vtk
>>> from vtk.util.misc import vtkGetDataRoot
>>> VTK_DATA_ROOT = vtkGetDataRoot()
>>>
>>> # Create the standard renderer, render window and interactor
>>> ren = vtk.vtkRenderer()
>>> renWin = vtk.vtkRenderWindow()
>>> renWin.AddRenderer(ren)
>>> iren = vtk.vtkRenderWindowInteractor()
>>> iren.SetRenderWindow(renWin)
>>>
>>> # Create the reader for the data
>>> reader = vtk.vtkStructuredPointsReader()
>>> reader.SetFileName(VTK_DATA_ROOT + "/Data/ironProt.vtk")
>>>
>>> #*** voi ***
>>> reader.Update()
>>> extent = reader.GetOutput().GetWholeExtent()
>>> print 'extent:', extent
>>> voi = vtk.vtkExtractVOI()
>>> voi.SetInput(reader.GetOutput())
>>> reader = voi
>>>
>>> # Create transfer mapping scalar value to opacity
>>> opacityTransferFunction = vtk.vtkPiecewiseFunction()
>>> opacityTransferFunction.AddPoint(20, 0.0)
>>> opacityTransferFunction.AddPoint(255, 0.2)
>>>
>>> # Create transfer mapping scalar value to color
>>> colorTransferFunction = vtk.vtkColorTransferFunction()
>>> colorTransferFunction.AddRGBPoint(0.0, 0.0, 0.0, 0.0)
>>> colorTransferFunction.AddRGBPoint(64.0, 1.0, 0.0, 0.0)
>>> colorTransferFunction.AddRGBPoint(128.0, 0.0, 0.0, 1.0)
>>> colorTransferFunction.AddRGBPoint(192.0, 0.0, 1.0, 0.0)
>>> colorTransferFunction.AddRGBPoint(255.0, 0.0, 0.2, 0.0)
>>>
>>> # The property describes how the data will look
>>> volumeProperty = vtk.vtkVolumeProperty()
>>> volumeProperty.SetColor(colorTransferFunction)
>>> volumeProperty.SetScalarOpacity(opacityTransferFunction)
>>> volumeProperty.ShadeOn()
>>> volumeProperty.SetInterpolationTypeToLinear()
>>>
>>> # The mapper / ray cast function know how to render the data
>>> compositeFunction = vtk.vtkVolumeRayCastCompositeFunction()
>>> volumeMapper = vtk.vtkVolumeRayCastMapper()
>>> volumeMapper.SetVolumeRayCastFunction(compositeFunction)
>>> volumeMapper.SetInput(reader.GetOutput())
>>>
>>> # The volume holds the mapper and the property and
>>> # can be used to position/orient the volume
>>> volume = vtk.vtkVolume()
>>> volume.SetMapper(volumeMapper)
>>> volume.SetProperty(volumeProperty)
>>>
>>> #*** outline ***
>>> outline = vtk.vtkOutlineFilter()
>>> outline.SetInput(reader.GetOutput())
>>> olmapper = vtk.vtkPolyDataMapper()
>>> olmapper.SetInput(outline.GetOutput())
>>> olactor = vtk.vtkActor()
>>> olactor.SetMapper(olmapper)
>>> olactor.GetProperty().SetColor(0,0,0)
>>> ren.AddActor(olactor)
>>>
>>> ren.AddVolume(volume)
>>> ren.SetBackground(1, 1, 1)
>>> renWin.SetSize(600, 600)
>>> renWin.Render()
>>>
>>> def CheckAbort(obj, event):
>>>    if obj.GetEventPending() != 0:
>>>        obj.SetAbortRender(1)
>>>
>>> def keypress(obj, event):
>>>    print 'key pressed'
>>>    newext = list(extent)
>>>    for i in range(0, 6, 2):
>>>        newext[i] = (newext[i] + newext[i+1]) / 2
>>>    print 'new extent:', newext
>>>    voi.SetVOI(*newext)
>>>    #ren.ResetCamera()
>>>    #ren.ResetCameraClippingRange()
>>>    renWin.Render()
>>>
>>> renWin.AddObserver("AbortCheckEvent", CheckAbort)
>>> iren.AddObserver("KeyPressEvent", keypress)
>>>
>>> iren.Initialize()
>>> renWin.Render()
>>> iren.Start()
>>>
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>>
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> 
> 
> 
>> << linux.png >>
> 
> 
> 
>> << windows.png >>
> 
> 
> 
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-- 
Dominik Szczerba, Dr.
Computer Vision Lab CH-8092 Zurich
http://www.vision.ee.ethz.ch/~domi