Discussion:
[vtkusers] Volume rendering - cannot make the image semi-transparecy
caseywang777
2018-11-20 19:30:01 UTC
Permalink
Hi,

I am using VTK to do volume rendering for IEEE SciVis 2018 contest.
This is the time step I am using,
http://oceans11.lanl.gov/deepwaterimpact/yA31/300x300x300-FourScalars_resolution/pv_insitu_300x300x300_30068.vti

I found that I cannot make the data (semi)transparent even if I have
already set the opacity to very low (lower than 0.001).
My question is how can I make it transparent? Or do I do anything wrong?

The following is the code (Python-vtk)


import vtk
import numpy as np
import vtk.util.numpy_support as VN

fileName = '/home/caseywang777/Downloads/pv_insitu_300x300x300_30068.vti'
#download from
http://oceans11.lanl.gov/deepwaterimpact/yA31/300x300x300-FourScalars_resolution/pv_insitu_300x300x300_30068.vti

colors = vtk.vtkNamedColors()
ren1 = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren1)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

# Create the reader for the data.
# reader = vtk.vtkStructuredPointsReader()
# reader.SetFileName(fileName)
# Create the reader for the data
reader = vtk.vtkXMLImageDataReader()
reader.SetFileName(fileName)
reader.Update()

# specify the data array in the file to process
reader.GetOutput().GetPointData().SetActiveAttribute('v02',0)

# convert the data array to numpy array and get the min and maximum valule
dary = VN.vtk_to_numpy(reader.GetOutput().GetPointData().GetScalars('v02'))
dMax = np.amax(dary) #data min value
dMin = np.amin(dary) #data max value
dRange = dMax - dMin

# Create transfer mapping scalar value to opacity.
opacityTransferFunction = vtk.vtkPiecewiseFunction()
opacityTransferFunction.AddPoint(dMin, 0.0)
#opacityTransferFunction.AddPoint(dMin + dRange/2, 0.005)
opacityTransferFunction.AddPoint(dMax, 0.001) ###### very small, still
opaque

# Create transfer mapping scalar value to color.
colorTransferFunction = vtk.vtkColorTransferFunction()
colorTransferFunction.AddRGBPoint(dMin, 0.2, 0.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*1, 1.0, 0.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*2, 0.0, 0.0, 1.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*3, 0.0, 1.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*4, 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.
# volumeMapper = vtk.vtkFixedPointVolumeRayCastMapper() # too slow? does
not work?
volumeMapper = vtk.vtkGPUVolumeRayCastMapper()
volumeMapper.SetInputConnection(reader.GetOutputPort())

# 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)

ren1.AddVolume(volume)
ren1.SetBackground(colors.GetColor3d("Wheat"))
ren1.GetActiveCamera().Azimuth(45)
ren1.GetActiveCamera().Elevation(30)
ren1.ResetCameraClippingRange()
ren1.ResetCamera()

renWin.SetSize(600, 600)
renWin.Render()

iren.Start()



Thanks foro you help!!




--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
_______________________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html

Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ

Search the list archives at: http://markmail.org/search/?q=vtkusers

Follow this link to subscribe/unsubscribe:
https://public.kitware.com/mailman/listinfo/vtkusers
Elvis Stansvik
2018-11-20 19:54:48 UTC
Permalink
I haven't finished downloading all of your example data file yet, but
I can already see that it has a very large Spacing:

[***@newton Hämtningar]$ head pv_insitu_300x300x300_30068.vti.part
<VTKFile type="ImageData" version="2.1" byte_order="LittleEndian"
header_type="UInt64" compressor="vtkZLibDataCompressor">
<ImageData WholeExtent="0 299 0 299 0 299" Origin="-2300000 -500000
-1200000" Spacing="15384.615385 9364.548495 8026.7558528">
<FieldData>
<DataArray type="Float32" Name="xrage_version" NumberOfTuples="1"
format="ascii">
1604.21
</DataArray>
<DataArray type="Int32" Name="cycle_index" NumberOfTuples="1"
format="ascii" RangeMin="0" RangeMax="0">
30068
</DataArray>
<DataArray type="Float32" Name="simulated_time" NumberOfTuples="1"
format="ascii" RangeMin="0" RangeMax="0">
[***@newton Hämtningar]$

Try adjusting the ScalarOpacityUnitDistance of your vtkVolumeProperty
to account for this. E.g. set it to something like 10000.

See the docs for that property for more info:

https://www.vtk.org/doc/nightly/html/classvtkVolumeProperty.html#a7dfb2d52c36821254ed078ce00cdab2a

"Set/Get the unit distance on which the scalar opacity transfer
function is defined. By default this is 1.0, meaning that over a
distance of 1.0 units, a given opacity (from the transfer function) is
accumulated. This is adjusted for the actual sampling distance during
rendering."

Elvis
Post by caseywang777
Hi,
I am using VTK to do volume rendering for IEEE SciVis 2018 contest.
This is the time step I am using,
http://oceans11.lanl.gov/deepwaterimpact/yA31/300x300x300-FourScalars_resolution/pv_insitu_300x300x300_30068.vti
I found that I cannot make the data (semi)transparent even if I have
already set the opacity to very low (lower than 0.001).
My question is how can I make it transparent? Or do I do anything wrong?
The following is the code (Python-vtk)
import vtk
import numpy as np
import vtk.util.numpy_support as VN
fileName = '/home/caseywang777/Downloads/pv_insitu_300x300x300_30068.vti'
#download from
http://oceans11.lanl.gov/deepwaterimpact/yA31/300x300x300-FourScalars_resolution/pv_insitu_300x300x300_30068.vti
colors = vtk.vtkNamedColors()
ren1 = vtk.vtkRenderer()
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren1)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
# Create the reader for the data.
# reader = vtk.vtkStructuredPointsReader()
# reader.SetFileName(fileName)
# Create the reader for the data
reader = vtk.vtkXMLImageDataReader()
reader.SetFileName(fileName)
reader.Update()
# specify the data array in the file to process
reader.GetOutput().GetPointData().SetActiveAttribute('v02',0)
# convert the data array to numpy array and get the min and maximum valule
dary = VN.vtk_to_numpy(reader.GetOutput().GetPointData().GetScalars('v02'))
dMax = np.amax(dary) #data min value
dMin = np.amin(dary) #data max value
dRange = dMax - dMin
# Create transfer mapping scalar value to opacity.
opacityTransferFunction = vtk.vtkPiecewiseFunction()
opacityTransferFunction.AddPoint(dMin, 0.0)
#opacityTransferFunction.AddPoint(dMin + dRange/2, 0.005)
opacityTransferFunction.AddPoint(dMax, 0.001) ###### very small, still
opaque
# Create transfer mapping scalar value to color.
colorTransferFunction = vtk.vtkColorTransferFunction()
colorTransferFunction.AddRGBPoint(dMin, 0.2, 0.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*1, 1.0, 0.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*2, 0.0, 0.0, 1.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*3, 0.0, 1.0, 0.0)
colorTransferFunction.AddRGBPoint(dMin + (dRange/4)*4, 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.
# volumeMapper = vtk.vtkFixedPointVolumeRayCastMapper() # too slow? does
not work?
volumeMapper = vtk.vtkGPUVolumeRayCastMapper()
volumeMapper.SetInputConnection(reader.GetOutputPort())
# 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)
ren1.AddVolume(volume)
ren1.SetBackground(colors.GetColor3d("Wheat"))
ren1.GetActiveCamera().Azimuth(45)
ren1.GetActiveCamera().Elevation(30)
ren1.ResetCameraClippingRange()
ren1.ResetCamera()
renWin.SetSize(600, 600)
renWin.Render()
iren.Start()
Thanks foro you help!!
--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
Search the list archives at: http://markmail.org/search/?q=vtkusers
https://public.kitware.com/mailman/listinfo/vtkusers
_______________________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html

Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ

Search the list archives at: http://markmail.org/search/?q=vtkusers

Follow this link to subscribe/unsubscribe:
https://public.kitware.com/mailman/listinfo
caseywang777
2018-11-20 20:06:00 UTC
Permalink
Hi, Elvis,

Yes, this solves my problem. :)

Thank you very much,
Bests,
KC




--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
_______________________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html

Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ

Search the list archives at: http://markmail.org/search/?q=vtkusers

Follow this link to subscribe/unsubscribe:
https://public.kitware.com/mailman/listinfo/vtkusers
Elvis Stansvik
2018-11-20 20:09:41 UTC
Permalink
Post by caseywang777
Hi, Elvis,
Yes, this solves my problem. :)
Thank you very much,
No problem, glad it worked out.

Cheers,
Elvis
Post by caseywang777
Bests,
KC
--
Sent from: http://vtk.1045678.n5.nabble.com/VTK-Users-f1224199.html
_______________________________________________
Powered by www.kitware.com
Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
Search the list archives at: http://markmail.org/search/?q=vtkusers
https://public.kitware.com/mailman/listinfo/vtkusers
_______________________________________________
Powered by www.kitware.com

Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html

Please keep messages on-topic and check the VTK FAQ at: http://www.vtk.org/Wiki/VTK_FAQ

Search the list archives at: http://markmail.org/search/?q=vtkusers

Follow this link to subscribe/unsubscribe:
https://public.kitware.com/mailman/listinfo/vtkusers

Loading...