[Insight-users] questions about generate and display sparse point cloud

[Luis Ibanez]

Hi Shaohua,

You could use the FastMarchingLevelSet class in
order to create a LevelSet from your set of points.

FastMarching accepts a list of seed points as input.
This is described in the SoftwareGuide
       http://www . itk . org/ItkSoftwareGuide . pdf
Section 9.3.1, pdf-page 365, paper-page 339.

About Generic Programming, you may want to take
a look at the book:

   "Generic Programming and the STL"
   by Matthew H. Austern




   Luis


--------------------
Shaohua Fan wrote:
> Hi Luis,
> 
> Thank you very much for answering my questions. I
> enclosed the VTK file behind. I will take your advices
> and generate/display the sparse points that way.
> Currently I just want to get my program run and see
> something on the screen, instead of worrying about the
> efficiency:-). 
> 
> I am writing some codes to approximate a 3D surface
> using level set method from a point cloud input. The
> sample and application codes in ITK seem either for
> segmentation or registration, not one for 3D
> reconstruction. The deformation in the
> SimpleLevelSetsExample only use regular geometric
> objects, i.e. those can be represented with analytical
> form. I am not sure how to efficiently update the
> distance funciton for irregular surface yet. Do you
> have some suggestions about what application codes I
> should look into which may be helpful for my project?
> 
> A side question: I think I have quite extensive c++
> programming experience, but still feel kind of
> difficult to write my own codes in ITk( I have some
> STL experience, no generic programming experience).
> What would be a relatively easy way for me to start? 
> -- I scanned the ITK user manual and am reading a book
> about generic programming.
> 
> Thanks,
> 
> Shaohua
> 
> ==============
> viewSparsePointsVTK.tcl
> 
> package require vtkinteraction
> 
> set X 63
> set Y 63
> set Z 63
> 
> #
> #  This script renders the initial and the final
> images from
> #  itk3DSimpleLevelSetsExample.  The zero level set is
> the 
> #  surface of interest.
> #
> #
> 
> set img_data1 "sparse_spherePoints_3D.raw"
> 
> vtkImageReader imgReader1
> imgReader1 SetDataExtent 0 $X 0 $Y 0 $Z
> imgReader1 SetFileName $img_data1
> imgReader1 SetDataByteOrderToLittleEndian
> imgReader1 SetNumberOfScalarComponents 1
> imgReader1 SetFileDimensionality 3
> imgReader1 SetDataScalarTypeToFloat
> 
>  vtkContourFilter marcher1
>  marcher1 SetNumberOfContours 1
>  marcher1 SetValue 0 0.0
>  marcher1 SetInput [imgReader1 GetOutput]
> 
> vtkOpenGLPolyDataMapper map1
>  map1 ScalarVisibilityOff
>  map1 ImmediateModeRenderingOn
>  map1 SetInput [marcher1 GetOutput]
> 
> vtkRenderer ren1
>   ren1 SetViewport 0 0 1 1
> 
> vtkRenderWindow renWin1
>   renWin1 AddRenderer ren1
>   renWin1 SetSize 256 256
> 
> vtkActor blob1
>  blob1 SetMapper map1
>  eval [blob1 GetProperty] SetColor 1.0 0.8 0.5
> 
> ren1 AddActor blob1
> 
> 
> frame .windows
> frame .buttons
> 
> vtkTkRenderWidget .windows.r1 -width 256 -height 256
> -rw renWin1
> pack .windows.r1 -side left -expand true -fill both
> -padx 1 -pady 1
> 
> pack .windows .buttons -expand true -fill both
> 
> BindTkRenderWidget .windows.r1
> 
> 
> --- Luis Ibanez <luis . ibanez at kitware . com> wrote:
> 
>>Hi Shaohua
>>
>>
>>    You will have to post the code of the VTK
>>pipeline
>>    that you are using for visualization if you want
>>to
>>    get some guidance on it.
>>
>>    Without lookit at the code it is quite hard to
>>figure
>>    out why you see are seeing a mesh and not a set
>>of
>>    points.    :-)
>>
>>    Your attached program only contains the ITK code
>>    related to the generation of the sparse points.
>>
>>---
>>
>>    Why do you want to visualize the spare points as
>>an image ?
>>
>>    You probably will get better performance by
>>saving
>>    the coordinates of the spare points and loading
>>them in a
>>
>>    vtkPolyData
>>   
>>
> 
> http://www . vtk . org/doc/nightly/html/classvtkPolyData . html
> 
>>    then pass them to a Glyp filter
>>   
>>
> 
> http://www . vtk . org/doc/nightly/html/classvtkGlyph3D . html
> 
>>
>>
>>Some lateral advice:
>>
>>    in lines 177 to 190 you are initializing the
>>image
>>    to a value using three nested for-loops and
>>SetPixel().
>>    This is very, very inefficient. You can simple
>>invoke
>>
>>              image->FillBuffer(  value );
>>
>>    or,
>>    use an ImageRegioniterator and a single while
>>loop.
>>    (FillBuffer will be faster anyways).
>>
>>
>>
>>
>>     You will get a better interface to VTK if you
>>     save the image in VTK format instead of RAW.
>>
>>     You can save in VTK format by simply using the
>>     extension ".vtk" in the filename. You don't
>>     even need to explicitly instantiate a
>>VTKImageIO
>>     class.
>>
>>
>>
>>
>>
>>Regards,
>>
>>
>>
>>      Luis
>>
> 
> 
> 
> 
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