[Insight-users] about Bspline

[Luis Ibanez]

Hi Yixun,



You seem to be mixing two different problems here.



First you asked for a way of creating a BSpline
for interpolating a surface,now you are asking
about performing BSpline deformable registration
between two point clouds.



The first problem:  creating a BSpline interpolation
                     from a point cloud, can be solved
                     with the BSpline interpolator available
                     in ITK, given that you confirmed that
                     your points are arranged topologically
                     in a 2D grid.


The Second (new) problem:  How to register two point clouds
                     using BSpline deformable registration,
                     is pretty much independent from the first
                     problem. In order to perform a registration
                     with a BSpline transform you don't need to
                     create interpolating surfaces in your point
                     cloud.



You seems to have a couple of misperceptions about the ITK
registration framework. Hopefully the following statements
will help you to clarify your perception.



1) The BSplines in ITK are N-Dimensional.
    The are not limited to 3D.


2) If you want to interpolate a surface over a
    point cloud in 3D, you pass 3 images that are 2D to
    the BSpline interpolator. Since your  points are
    topologically equivalent to the grid nodes of this 2D image,
    you need three images where the pixel values are associated
    to the X, Y  and Z coordinates of your points respectively.


3) You don't need to generate an interpolating surface in order
    to register the point clouds, *unless* your cloud is so
    scattered that there are wide gaps in the points.


4) You don't need deformable registration in order to
    register two point clouds taken from a range scanner.

    You probably can do this registration by using directly
    the code in:


        Insight/Examples/Patented/
                  IterativeClosestPoint2.cxx
                  IterativeClosestPoint3.cxx


    You will need, of course, to provide a good initialization
    for the transform.





   Regards,



       Luis



---------------
Yixun Liu wrote:

> Thank your reply!
> 
> The point cloud is acquired by a Laser range scanner, so the points should be arranged topologically in a 2D grid embeded in 3D space. If I represent this point cloud with a 2D B-Spline, can I non-rigidly  register this B-Spline surface with another point cloud? In my opinion, ITK only support 3D B-Spline when two point cloud need be non-rigidly registered.
> 
> Regards,
> 
> Yixun Liu
> 
> 
> ----- Original Message ----- 
> From: "Luis Ibanez" <luis.ibanez at kitware.com>
> To: "Yixun Liu" <yxliu at fudan.edu.cn>
> Cc: "VTK" <vtkusers at vtk.org>; <insight-users at itk.org>
> Sent: Friday, May 27, 2005 12:50 AM
> Subject: Re: [Insight-users] about Bspline
> 
> 
> 
>>Hi Yixun,
>>
>>
>>Are your points arranged topologically
>>in a 2D grid embebded in 3D space ?
>>
>>
>>If YES,
>>then you can use the BSpline classes
>>in ITK for this purpose.
>>
>>http://www.itk.org/Insight/Doxygen/html/classitk_1_1BSplineInterpolateImageFunction.html
>>
>>
>>
>>If NO,
>>then you have the option of using KernelBased Splines
>>(five different types are available in ITK).
>>
>>http://www.itk.org/Insight/Doxygen/html/classitk_1_1KernelTransform.html
>>
>>
>>
>>
>> Regards,
>>
>>
>>
>>    Luis
>>
>>
>>----------------------
>>Yixun Liu wrote:
>>
>>
>>>Hi,
>>> 
>>>I have a surface represented by point cloud. I need to generate a 2D 
>>>B-Spline from this point cloud. Dose ITK or VTK support it?
>>> 
>>> 
>>>Best regards,
>>> 
>>>Yixun Liu
>>>
>>>
>>>------------------------------------------------------------------------
>>>
>>>_______________________________________________
>>>Insight-users mailing list
>>>Insight-users at itk.org
>>>http://www.itk.org/mailman/listinfo/insight-users
>>
>>
>>
>>
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