[vtkusers] Find point by coordiante

[Boehm, Lukas]

Thank you very much! This example solved my problem :-) 

 

My vtkImageData is only for 2D and z-value for spacing was set to 0. I set it to 1 and now it works.

 

Good bye,

Lukas

 

From: Gonzalo Amadio [mailto:gonzaloamadio at gmail.com] 
Sent: Dienstag, 21. August 2012 17:48
To: Boehm, Lukas
Cc: Kevin H. Hobbs; vtkusers at vtk.org
Subject: Re: [vtkusers] Find point by coordiante

 

Here do you have an example. Where findPoint is used either in an image and in a polydata.

 

 

 

#include <vtkVersion.h>

#include <vtkSmartPointer.h>

#include <vtkPolyData.h>

#include <vtkTriangleFilter.h>

#include <vtkIdTypeArray.h>

#include <vtkImageDataGeometryFilter.h>

#include <vtkImageData.h>

 

 

int main(int, char *[])

{

            //Create an image data

            vtkSmartPointer<vtkImageData> imageData = vtkSmartPointer<vtkImageData>::New();

            imageData->SetDimensions(5,5,1);

            imageData->SetSpacing(1.0, 1.0, 1.0);

            imageData->SetOrigin(0.0, 0.0, 0.0);

 

            //Convert the image to a polydata

            vtkSmartPointer<vtkImageDataGeometryFilter> imageDataGeometryFilter = vtkSmartPointer<vtkImageDataGeometryFilter>::New();

            imageDataGeometryFilter->SetInputConnection(imageData->GetProducerPort());

            imageDataGeometryFilter->Update();

 

            vtkSmartPointer<vtkTriangleFilter> triangleFilter = vtkSmartPointer<vtkTriangleFilter>::New();

            triangleFilter->SetInputConnection(imageDataGeometryFilter->GetOutputPort());

            triangleFilter->Update();

 

            vtkSmartPointer<vtkPolyData> triang = triangleFilter->GetOutput();//polydata normal, cells

 

            triang->BuildLinks();

            triang->BuildCells();

 

            vtkIdType id = triang->FindPoint(0,0,0);

            std::cout << id << std::endl;

 

            vtkIdType id2 = imageData->FindPoint(0,0,0);

            std::cout << id2 << std::endl;

 

            return EXIT_SUCCESS;

 

}

 

2012/8/21 Boehm, Lukas <Lukas.Boehm at cellent.de>

Thank you both for your answers!

 

FindPoint works perfect with vtkPolyData, but now I think I can't use vtkPolyData. Instead I probably have to use vtkImageData. 

 

My VTK pipeline looks like this:

 

1.)   Create vtkImageData with all points

2.)   Use vtkMarchingSquares filter to get vtkPolyData representing some iso lines

3.)   Some unimportant clipping stuff...

 

If I use the vtkPolyData object from vtkMarchingSquares I get values which make sense. But it seems like marching squares removes all points where no iso lines are drawn. I only find ids of points which are on the iso lines. 

 

So my idea was to use vtkImageData. But not even the simpliest example works with vtkImageData and FindPoint:

 

double[] pos = imageData.GetPoint(200);

// pos contains 18.0, -29.0, 0.0 which seems to be correct

int id = imageData.FindPoint(pos[0], pos[1], pos[2]);

 

I would expect 'id' to have the value 200. But it always has the value -1. The documentation says that a return value < 0 means that the point can't be found (maybe it's outside of the vtkImageData object). Could somebody please tell me why FindPoint always returns -1?

 

Thank you,

Lukas

 

From: Gonzalo Amadio [mailto:gonzaloamadio at gmail.com] 
Sent: Dienstag, 21. August 2012 15:48
To: Kevin H. Hobbs
Cc: Boehm, Lukas; vtkusers at vtk.org
Subject: Re: [vtkusers] Find point by coordiante

 

I think this will work!..

http://www.vtk.org/doc/release/5.6/html/a00430.html#fb20db494bf2e8c0aff4ff2fcf7d6a22

The doc says "find the closes point to the coordinates provided as arguiment"

2012/8/21 Kevin H. Hobbs <hobbsk at ohio.edu>

On 08/21/2012 09:18 AM, Boehm, Lukas wrote:
> Hello,
>
>
>
> I've got a short question. I have a vtkPoints object and a coordinate
> (x,y,z). Is there a way to get the id of the closest point to this
> coordinate? I didn't find anything.
>

You need a point locator.

http://www.vtk.org/doc/nightly/html/classvtkPointLocator.html


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-- 
--------
Gonzalo Amadio

 

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-- 
--------
Gonzalo Amadio

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