How to set colors for PointData of vtkStructuredGrid example

Hi,

I’m beginner. I read tutorial and watch examples but some basic questions still actual.
So here is simple example of vtkStructuredGrid. I’m trying to add data to the points and display this data as color. The problem that this modified example doesn’t work. As a result my displayed data is the same as in the picture from the example link. Please, give me a hint what I’am doing wrong?
Here is my modified code:

#include <vtkSmartPointer.h>
#include <vtkStructuredGrid.h>
#include <vtkXMLStructuredGridWriter.h>
#include <vtkDataSetMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkDoubleArray.h>
#include <vtkFloatArray.h>
#include <vtkLookupTable.h>
#include <vtkScalarBarActor.h>
#include <vtkPointData.h>

int main(int, char *[])
{
  // Create a grid
  vtkSmartPointer<vtkStructuredGrid> structuredGrid =
    vtkSmartPointer<vtkStructuredGrid>::New();

  vtkSmartPointer<vtkPoints> points =
    vtkSmartPointer<vtkPoints>::New();
  vtkDoubleArray *array = vtkDoubleArray::New();

  size_t nx = 2, ny = 3, nz = 2;
  double x, y, z;

  x = 0.0;
  y = 0.0;
  z = 0.0;

  for (size_t i = 0; i < nx*ny*nz; i++){
      array->InsertNextValue(i);
  }

  for(unsigned int k = 0; k < nz; k++)
  {
    z += 2.0;
    for(unsigned int j = 0; j < ny; j++)
    {
      y += 1.0;
      for(unsigned int i = 0; i < nx; i++)
      {
        x += .5;
        points->InsertNextPoint(x, y, z);
      }
    }
  }

  // Specify the dimensions of the grid
  structuredGrid->SetDimensions(nx,ny,nz);
  structuredGrid->SetPoints(points);
  structuredGrid->GetPointData()->AddArray(array);

  int* dims = structuredGrid->GetDimensions();

  // Retrieve the entries from the grid and print them to the screen
  unsigned int counter = 0;

  for (int k = 0; k < dims[2]; k++)
  {
    for (int j = 0; j < dims[1]; j++)
    {
      for (int i = 0; i < dims[0]; i++)
      {
        double p[3];
        structuredGrid->GetPoint(counter, p);

        double pNew[3];
        structuredGrid->GetPoint(i, j, k, pNew);

        std::cout << "P   : "
                  << p[0] << " "
                  << p[1] << " "
                  << p[2] << std::endl;
        std::cout << "PNew: "
                  << pNew[0] << " "
                  << pNew[1] << " "
                  << pNew[2] << std::endl;

        counter++;
      }
    }
  }

  // Map the scalar values in the image to colors with a lookup table:
  vtkSmartPointer<vtkLookupTable> lookupTable =
          vtkSmartPointer<vtkLookupTable>::New();
  //lookupTable->SetRange(0.0, nx*ny*nz); // image intensity range
  //lookupTable->SetValueRange(0.0, nx*ny*nz); // from black to white
  lookupTable->SetTableRange(0, nx*ny*nz);
  //lookupTable->SetSaturationRange(0.0, nx*ny*nz); // no color saturation
  //lookupTable->SetNumberOfTableValues(256);
  lookupTable->SetRampToLinear();
  lookupTable->Build();

  // Create a mapper and actor
  vtkSmartPointer<vtkDataSetMapper> mapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  mapper->SetInputData(structuredGrid);
  mapper->SetLookupTable(lookupTable);

  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);

  // Create a renderer, render window, and interactor
  vtkSmartPointer<vtkRenderer> renderer =
    vtkSmartPointer<vtkRenderer>::New();
  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->SetBackground(.3, .6, .3); // Background color green

  // Render and interact
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

Best regards,
kerim

Here is a simplified solution that you can use StructuredGrid.cxx (3.1 KB) . Here you have the choice of colouring either by point data or cell data.

If you need it, this is the CMake file to useCMakeLists.txt (2.7 KB) :

2 Likes

Thank for working example! It really helped