[vtkusers] Combining three velocity components
Adam Wiktor
awiktor at emory.edu
Mon Aug 3 09:29:57 EDT 2009
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:
>> http://www.vtk.org/Wiki/VTK_FAQ
>>
>> Follow this link to subscribe/unsubscribe:
>> http://www.vtk.org/mailman/listinfo/vtkusers
>>
>>
>>
>>
>> -- 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20090803/cf3af450/attachment.htm>
More information about the vtkusers
mailing list