[vtkusers] Find point by coordiante

[Gonzalo Amadio]

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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