[vtkusers] Fwd: Re: Extract isosurfaces from a point cloud polydata with contourfilter
Bill Lorensen
bill.lorensen at gmail.com
Sun Jan 18 08:23:50 EST 2015
Cubes would work (vtkHexahedron).
On Sun, Jan 18, 2015 at 8:04 AM, Daniel Coelho <1danielcoelho at gmail.com> wrote:
> ---------- Forwarded message ----------
> From: "Daniel Coelho" <1danielcoelho at gmail.com>
> Date: Jan 18, 2015 2:03 PM
> Subject: Re: [vtkusers] Extract isosurfaces from a point cloud polydata with
> contourfilter
> To: "Bill Lorensen" <bill.lorensen at gmail.com>
> Cc:
>
> Thanks for the quick reply!
>
> I use some polydata algorithms on this data, so it wouldn't be efficient to
> keep switching back and forth all the time.
>
> How could I make my cells then? Would it suffice to make them cubes, where
> the vertices are the vertices of each cube? I've never really understood how
> cells work. Even the VTK books don't really help, sadly
>
> On Jan 18, 2015 1:47 PM, "Bill Lorensen" <bill.lorensen at gmail.com> wrote:
>>
>> VertexGlyphFilter generates vertex cells. These cells are points. You
>> cannot contour vertices. You need to create cells that have area or
>> volume. In your case, it your points are defined on a uniform lattice,
>> you can create an ImageData that you can contour.
>>
>>
>> On Sun, Jan 18, 2015 at 7:01 AM, Daniel Coelho <1danielcoelho at gmail.com>
>> wrote:
>> > Hello everyone!
>> >
>> > I have a point cloud in the form of a polydata, where I build vertices
>> > with
>> > vtkVertexGlyphFilter.
>> >
>> > That polydata has pointdata with scalars ranging from 0 to 255, and I'm
>> > trying to use vtkContourFilter to extract 5 planes, that ideally should
>> > cut
>> > through the data at the values corresponding to each plane.
>> >
>> > Just to make it clearer: The expected output should be 5 parallel
>> > planes,
>> > equidistant to each other, where each is an isosurface of a certain
>> > value,
>> > with respect to the scalars of the pointcloud.
>> >
>> > The problem is: I get absolutely no output. No points, no cell, nada.
>> > I've
>> > looked at every example I could find and the mailing list archive, but
>> > couldn't pinpoint the problem.
>> >
>> > Here is a short compilable example that shows this problem. You can also
>> > see
>> > outputs from print statements as comments:
>> > OBS: I use VTK 5.8 for some reasons, this is non-negotiable
>> >
>> > #include <vtkSmartPointer.h>
>> >
>> > #include <vtkContourFilter.h>
>> >
>> > #include <vtkTypeUInt8Array.h>
>> >
>> > #include <vtkVertexGlyphFilter.h>
>> >
>> > #include <vtkPolyDataMapper.h>
>> >
>> > #include <vtkActor.h>
>> >
>> > #include <vtkRenderer.h>
>> >
>> > #include <vtkRenderWindow.h>
>> >
>> > #include <vtkRenderWindowInteractor.h>
>> >
>> >
>> > #define VTK_NEW(type, instance) \
>> >
>> > ; \
>> >
>> > vtkSmartPointer<type> instance = vtkSmartPointer<type>::New();
>> >
>> >
>> > int main(int argc, char *argv[]) {
>> >
>> >
>> > VTK_NEW(vtkPoints, points);
>> >
>> > points->Allocate(100 * 100 * 100);
>> >
>> >
>> > VTK_NEW(vtkTypeUInt8Array, data_array);
>> >
>> > data_array->Allocate(100 * 100 * 100);
>> >
>> >
>> > for (int x = 0; x < 100; x++) {
>> >
>> > for (int y = 0; y < 100; ++y) {
>> >
>> > for (int z = 0; z < 100; ++z) {
>> >
>> > points->InsertNextPoint(x, y, z);
>> >
>> > data_array->InsertNextValue(z % 256);
>> >
>> > }
>> >
>> > }
>> >
>> > }
>> >
>> >
>> > VTK_NEW(vtkPolyData, polydata);
>> >
>> > polydata->SetPoints(points);
>> >
>> > polydata->GetPointData()->SetScalars(data_array);
>> >
>> >
>> > VTK_NEW(vtkVertexGlyphFilter, glyph_filter);
>> >
>> > glyph_filter->SetInput(polydata);
>> >
>> > glyph_filter->Update();
>> >
>> > glyph_filter->GetOutput()->Print(std::cout << "Glyph filter: \n");
>> >
>> > //Output here:
>> >
>> > //Number Of Points: 1000000
>> >
>> > //Number Of Cells: 1000000
>> >
>> > //Bounds look good, all good
>> >
>> >
>> > VTK_NEW(vtkContourFilter, cont_filt);
>> >
>> > cont_filt->SetInputConnection(glyph_filter->GetOutputPort());
>> >
>> > double scalarRange[2];
>> >
>> > polydata->GetPointData()->GetScalars()->GetRange(scalarRange);
>> >
>> > cont_filt->GenerateValues(5, scalarRange[0], scalarRange[1]);
>> >
>> > cont_filt->Update();
>> >
>> >
>> > // Print the contours
>> >
>> > int num_contours = cont_filt->GetNumberOfContours();
>> >
>> > double cont_values[num_contours];
>> >
>> > cont_filt->GetValues(cont_values);
>> >
>> > std::cout << "Contours: ";
>> >
>> > for (int var = 0; var < num_contours; ++var) {
>> >
>> > std::cout << cont_values[var] << " ";
>> >
>> > }
>> >
>> > std::cout << std::endl;
>> >
>> > //Output here:
>> >
>> > //Contours: 0 24.75 49.5 74.25 99
>> >
>> >
>> > cont_filt->GetOutput()->Print(std::cout << "Contour filter: \n");
>> >
>> > //Output here:
>> >
>> > //No points, no cells, default bounds, no nothing
>> >
>> >
>> > VTK_NEW(vtkPolyDataMapper, mapper);
>> >
>> > mapper->SetInputConnection(cont_filt->GetOutputPort());
>> >
>> > mapper->SetScalarVisibility(1);
>> >
>> >
>> > VTK_NEW(vtkActor, actor);
>> >
>> > actor->SetMapper(mapper);
>> >
>> >
>> > VTK_NEW(vtkRenderer, renderer);
>> >
>> > renderer->AddActor(actor);
>> >
>> >
>> > VTK_NEW(vtkRenderWindow, render_window)
>> >
>> > render_window->AddRenderer(renderer);
>> >
>> > render_window->SetSize(600, 600);
>> >
>> >
>> > VTK_NEW(vtkRenderWindowInteractor, interactor);
>> >
>> > interactor->SetRenderWindow(render_window);
>> >
>> >
>> > renderer->ResetCamera();
>> >
>> > render_window->Render();
>> >
>> > interactor->Start();
>> >
>> > }
>> >
>> >
>> > _______________________________________________
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>> >
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>> >
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>> >
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>>
>>
>>
>> --
>> Unpaid intern in BillsBasement at noware dot com
>
>
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