[vtkusers] Combining three velocity components
Wes Turner
wes.turner at kitware.com
Mon Aug 3 10:35:39 EDT 2009
Adam,
It is not generating separate arrays. It is creating one array with 3
components per entry. It is not clear what you are trying to do, but at the
output of the append, what you have is an image where the pixel values are
stored as a single array: x[0], y[0], z[0], x[1], y[1], z[1], x[2], y[2],
z[2], ... , x[k-1], y[k-1], z[k-1] where x[i], y[i], and z[i] all represent
the values for the ith x, y or z component respectively and where k=m*n for
an m*n image.
- Wes
On Mon, Aug 3, 2009 at 9:29 AM, Adam Wiktor <awiktor at emory.edu> wrote:
> Yes, that's the formula for it, but what I can't figure out is the actual
> code for the calculator. After doing the ImageAppendComponents, I need to
> find a way for the calculator to do that operation on all three variables.
> Right now, it isn't recognizing the y and z components. How do I pass those
> two variables to the calculator so that it will recognize all three?
>
> This is what I have right now, but as I said, it only accepts the 'x'
> component and gives me an "invalid array name" error for the other two.
>
> append=vtk.vtkImageAppendComponents()
> append.AddInput(xcalc.GetOutput())
> append.AddInput(ycalc.GetOutput())
> append.AddInput(zcalc.GetOutput())
> append.Update()
>
> velcalc = vtk.vtkArrayCalculator()
> velcalc.SetInput(append.GetOutput())
> velcalc.AddVectorArrayName("x", 0, 1, 2)
> velcalc.AddVectorArrayName("y", 0, 1, 2)
> velcalc.AddVectorArrayName("z", 0, 1, 2)
> velcalc.SetResultArrayName("Velocity")
> velcalc.SetFunction("x+y+z")
> velcalc.Update()
>
> Thanks,
>
> Adam
>
>
> On Fri, Jul 31, 2009 at 4:53 PM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:
>
>> u*iHat+v*jHat+w*kHat
>>
>> Adam Wiktor wrote:
>>
>>> Wes,
>>>
>>> The problem is that I need the overall velocity as a single vector, not
>>> the components. I think I still need the calculator to sum the three
>>> components to give the velocity. How would I do that?
>>>
>>> Thanks,
>>>
>>> Adam
>>>
>>> On Fri, Jul 31, 2009 at 3:58 PM, Wes Turner <wes.turner at kitware.com<mailto:
>>> wes.turner at kitware.com>> wrote:
>>>
>>> If you are just trying to get an image with three components
>>> corresponding to the x, y, and z, then that is what you should have
>>> as the output of the append filter. The data at that point is not
>>> stored in separate x, y, and z vectors, but is instead a single
>>> multicomponent image. You should have no need of the image
>>> calculator at that point.
>>>
>>> - Wes
>>>
>>>
>>> On Fri, Jul 31, 2009 at 3:24 PM, Adam Wiktor <awiktor at emory.edu
>>> <mailto:awiktor at emory.edu>> wrote:
>>>
>>> Yes, I tried both that and AppendFilter, but I'm still having
>>> problems. I may not be using the append correctly, but the
>>> calculator is only recognizing one of the three components, and
>>> I get this error message (it's the same for both
>>> ImageAppendComponents and AppendFilter):
>>>
>>> ERROR: In
>>> /home/awiktor/Desktop/VTK/Graphics/vtkArrayCalculator.cxx, line
>>> 338
>>> vtkArrayCalculator (0x763d70): Invalid array name: y
>>>
>>> I get the same message except with "Invalid array name: z" if I
>>> remove all references to y, so I think this means that the
>>> calculator isn't seeing the 'y' and 'z' variables.
>>>
>>> Here's the part of the code that isn't working:
>>>
>>> append=vtk.vtkImageAppendComponents()
>>> append.AddInput(xcalc.GetOutput())
>>> append.AddInput(ycalc.GetOutput())
>>> append.AddInput(zcalc.GetOutput())
>>> append.Update()
>>>
>>> velcalc = vtk.vtkArrayCalculator()
>>> velcalc.SetInput(append.GetOutput())
>>> velcalc.AddVectorArrayName("x", 0, 1, 2)
>>> velcalc.AddVectorArrayName("y", 0, 1, 2)
>>> velcalc.AddVectorArrayName("z", 0, 1, 2)
>>> velcalc.SetResultArrayName("Velocity")
>>> velcalc.SetFunction("x+y+z")
>>> velcalc.Update()
>>>
>>> Any idea what the problem is?
>>>
>>> Thanks,
>>>
>>> Adam
>>>
>>>
>>> On Fri, Jul 31, 2009 at 12:54 PM, Wes Turner
>>> <wes.turner at kitware.com <mailto:wes.turner at kitware.com>> wrote:
>>>
>>> Did you try ImageAppendComponents?
>>>
>>>
>>> http://www.vtk.org/doc/nightly/html/classvtkImageAppendComponents.html
>>>
>>> <
>>> http://www.vtk.org/doc/nightly/html/classvtkImageAppendComponents.html>-
>>> Wes
>>>
>>> On Fri, Jul 31, 2009 at 12:16 PM, Adam Wiktor
>>> <awiktor at emory.edu <mailto:awiktor at emory.edu>> wrote:
>>>
>>> Hi All,
>>>
>>> I am fairly new to VTK, so please bear with me. I'm
>>> trying to visualize blood flow in the aorta from MRI
>>> scans. The velocity data is stored in three separate vti
>>> images, for the x-, y- and z- components. Each image has
>>> a scalar variable 'DICOMImage' which is the speed in
>>> that direction. I need to combine the components into
>>> the overall velocity, which I will then import into
>>> paraview to add streamlines and other things.
>>>
>>> My original thought was to use the vtkArrayCalculator to
>>> multiply each image by the unit vector (for the x
>>> component, for example, it would be DICOMImage*iHat). I
>>> would then need to combine these vectors into the
>>> velocity with another calculator, just doing x+y+z. I
>>> might be able to simplify this by just using one
>>> calculator that did x*iHat + y*jHat + z*kHat, but I
>>> don't know how to change the variable names from
>>> DICOMImage to x, y, and z so that the calculator can
>>> distinguish between them.
>>>
>>> First of all, I'd like to know if there's an easier way
>>> of doing this.
>>>
>>> If there isn't a more straight-forward way, then the
>>> main thing I need to figure out is how to get the final
>>> calculator to use the three different inputs. What would
>>> be the best way to do that?
>>>
>>> Thanks for any help you can give!
>>>
>>> - Adam
>>> _______________________________________________
>>> Powered by www.kitware.com <http://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:
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>>> Follow this link to subscribe/unsubscribe:
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>>>
>>>
>>>
>>> -- Wesley D. Turner, Ph.D.
>>> Kitware, Inc.
>>> R&D Engineer
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065-8662
>>> Phone: 518-371-3971 x120
>>>
>>>
>>>
>>>
>>>
>>> -- Wesley D. Turner, Ph.D.
>>> Kitware, Inc.
>>> R&D Engineer
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065-8662
>>> Phone: 518-371-3971 x120
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> 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
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.vtk.org/mailman/listinfo/vtkusers
>>>
>>
>>
>> --
>> d o m i n i k s z c z e r b a , p h d . . . . . . . . . . .
>> c o m p u t a t i o n a l l i f e s c i e n c e g r o u p
>> . . . . . . . i t ' i s r e s e a r c h f o u n d a t i o n
>> . . . . . . . . . . . . . . . . . . . . http://www.itis.ethz.ch
>>
>>
>
--
Wesley D. Turner, Ph.D.
Kitware, Inc.
R&D Engineer
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-371-3971 x120
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