[vtkusers] coloring a sphere by elevation

[Liam Kurmos]

I'm creating an example to colour the surface of a sphere using a
lookup table, where the scalar value is just the value of one of the
vertex coords.
The code below essentially works but only shows 2 colors.

2Qs:

-why dont i see a range of colors from the lookup table?

-i thought i should be able to get the coordinates of a vertex from
the vtkPointData but i couldnt do this or find an example and had to
use vtkPolyData->getPoint(i). Is it straight forward to get down to
the points for pointdata?


any thoughts appreciated,


Liam




void Analyser4D::testFunc() {
    cout << " test code" << endl;

    vtkSmartPointer<vtkSphereSource> sphereSource =
vtkSmartPointer<vtkSphereSource>::New();
    float radius = 100000;
    sphereSource->SetCenter(0,0,0);
    sphereSource->SetRadius(radius);
    sphereSource->SetPhiResolution(20);
    sphereSource->SetThetaResolution(20);

    sphereSource->Update();

    vtkPolyData* polyd=sphereSource->GetOutput();
    vtkPointData* pointd=polyd->GetPointData();
    vtkSmartPointer<vtkFloatArray> scalars=
vtkSmartPointer<vtkFloatArray>::New();
    cout<<"point comps "<<pointd->GetNumberOfComponents()<<" tups
"<<pointd->GetNumberOfTuples()<<" arrays
"<<pointd->GetNumberOfArrays()<<endl;
    scalars->SetNumberOfValues(pointd->GetNumberOfTuples());
    scalars->SetName("scalars");
    for (int i=0;i<scalars->GetNumberOfTuples();i++){
        //vtkDataArray* dataa=pointd->GetArray(0);

        vtkFloatArray* dataa=vtkFloatArray::SafeDownCast(pointd->GetArray(0));
        double* point=polyd->GetPoint(i);
        scalars->SetValue(i,point[0]);

    }
    pointd->SetScalars(scalars);
    vtkLookupTable* lut=vtkLookupTable::New();
	lut->SetHueRange(0,0.6);		//Red to Blue
	lut->SetAlphaRange(1,1);
	lut->SetValueRange(1,1.0);
	lut->SetSaturationRange(1.0,1.0);
	lut->SetNumberOfTableValues(256*256*256);
	lut->SetRange(-100000,100000);//altering range appear not to effect output
	lut->Build();



//
     vtkSmartPointer<vtkPolyDataMapper> mapper =
vtkSmartPointer<vtkPolyDataMapper>::New();

    mapper->SetInputConnection(sphereSource->GetOutputPort());
    mapper->SetLookupTable(lut);
    vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
    actor->SetMapper(mapper);
    actor->GetProperty()->SetAmbient(1); //SetShading(0);
    actor->GetProperty()->SetDiffuse(0); //SetShading(0);
    actor->GetProperty()->SetSpecular(0); //SetShading(0);
    actor->GetProperty()->SetInterpolationToFlat();
//actor->GetProperty()->SetOpacity(0.5);
    actor->GetProperty()->SetColor(1, 0, 0);

//
    vtkSmartPointer<vtkRenderer> renderer;
    vtkSmartPointer<vtkRenderWindow> renderWindow;

    renderer = vtkSmartPointer<vtkRenderer>::New();
    renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
    renderer->SetBackground(0, 0, 0);
    renderWindow->AddRenderer(renderer);
    renderWindow->SetSize(300, 300);


    renderer->SetBackground(0, 0, 0);
    renderer->AddActor(actor);

    vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor
= vtkSmartPointer<vtkRenderWindowInteractor>::New();
  renderWindowInteractor->SetRenderWindow(renderWindow);
    renderWindow->Render();
  renderWindowInteractor->Start();

}