[vtkusers] Combining three velocity components

[Wes Turner]

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> 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>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> 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
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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
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