# Equalize the number of points two CenterlineComputationModels

**URL:** <https://discourse.slicer.org/t/equalize-the-number-of-points-two-centerlinecomputationmodels/3408>\
**Category:** Support\
**Created:** [July 7, 2018, 9:45am UTC](https://discourse.slicer.org/t/equalize-the-number-of-points-two-centerlinecomputationmodels/3408 "2018-07-07T09:45:13Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![shahrokh](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/shahrokh/32/1499_2.png) [@shahrokh](https://discourse.slicer.org/u/shahrokh)\
**Post date:** [July 7, 2018, 9:45am UTC](https://discourse.slicer.org/t/equalize-the-number-of-points-two-centerlinecomputationmodels/3408/1 "2018-07-07T09:45:13Z")

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Hi Slicer Developers

I have two models with the names of CenterlineComputationModelMR and CenterlineComputationModelCT with the following information:  
**CenterlineComputationModelMR**  
_Mesh Type: Surface Mesh (vtkPolyData)_  
_Surface Area: 0.00 mm2_  
_Volume: 0.00 mm3_  
_Number of Points: 177_

**CenterlineComputationModelCT**  
_Mesh Type: Surface Mesh (vtkPolyData)_  
_Surface Area: 0.00 mm2_  
_Volume: 0.00 mm3_  
_Number of Points: 277_

I want to make the same number of points such as 260 points. How can I do it?  
I need to do it(equalize the number of points) so I want use them as inputs to “Scattered Transform” modules.

Please guide me,  
Shahrokh

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<div class="post-metadata">

**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [July 9, 2018, 6:09pm UTC](https://discourse.slicer.org/t/equalize-the-number-of-points-two-centerlinecomputationmodels/3408/2 "2018-07-09T18:09:10Z")

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Determining point correspondences between two vessel trees is a difficult task. It is not just a matter of resampling a line.

Probably a more robust and simpler way would be to compute a distance map image from the trees and use intensity-based image registration to compute transform between them. These steps are performed by Segment registration extension. You just need to convert the input models to segments in a Segmentation node to be able to use it. Segmentations module import/export feature should be usable if the centerlines are tubular shapes. If centerlines are just lines then you can convert it to tubes by applying VTK tube filter.