Add temperature attribute using vtkDoubleArray->SetArray is not effect the result color

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1

Hi,
I am a beginner, when I my vtkUnstructuredGrid object have a attribute temperature, there are 2 methods to put it into vtkUnstructuredGrid object, one is that put 1 by 1 using InsertNextTuple1() , this method work well. the other is that put all at once using SetArray, all work well , but the result color is shown according to the input temperature?
this is my code:
void MainWindow::showCyScene()
{

double xyz[][3]={{0, 0 ,2 },
                 {1, 0 ,2 },
                 {1, 1 ,2 },
                 {0, 1 ,2 },
                 {2, 0 ,2 },
                 {3, 0 ,2 },
                 {3, 1 ,2 },
                 {2, 1 ,2 }};

vtkIdType cells[][3]={{0 ,1,2 },
                {0 ,2,3 },
                {1 ,4,2 },
                {4 ,7,2 },
                {4 ,5,7 },
                {5 ,6,7 }};

double temperature[8]={1.0 ,2.0 ,2.0 ,1.0,3.0, 4.0 ,4.0, 3.0};

vtkSmartPointer<vtkPoints> pts=vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkUnstructuredGrid> ug=vtkSmartPointer<vtkUnstructuredGrid>::New();

for(int i=0;i<8;i++)
    pts->InsertNextPoint(xyz[i]);
for (int i = 0; i < 6; ++i) {
    ug->InsertNextCell(VTK_TRIANGLE,3,cells[i]);
}

ug->SetPoints(pts);

vtkSmartPointer<vtkDoubleArray> da=vtkSmartPointer<vtkDoubleArray>::New();
da->SetName("temp");
da->SetArray(temperature,8,1);   //Method 1： using SetArray() add temperature at once is not effective.

// for(int i=0;i<8;i++)
// da->InsertNextTuple1(temperature[i]); //Method 2： using InsertNextTuple() add temperature 1 by 1 is effective.

ug->GetPointData()->SetScalars(da);
qDebug()<<ug->GetPointData()->GetArrayName(0);
ug->GetPointData()->SetActiveScalars("temp");


vtkSmartPointer<vtkLookupTable> lut=vtkSmartPointer<vtkLookupTable>::New();
lut->SetNumberOfColors(3);
lut->SetTableValue(0,1,1,1);
lut->SetTableValue(1,0,1,0);
lut->SetTableValue(2,0,0,1);
lut->Build();

vtkSmartPointer<vtkDataSetMapper> mapper=vtkSmartPointer<vtkDataSetMapper>::New();
mapper->SetInputData(ug);

mapper->SetScalarRange(1.0,5.0);
mapper->SetLookupTable(lut);
mapper->ScalarVisibilityOn();
mapper->SetScalarModeToUsePointData();

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

vtkSmartPointer<vtkRenderer> renderer=
        vtkSmartPointer<vtkRenderer>::New();
renderer->SetBackground(1,1,1);

renderer->AddActor(actor);

vtkSmartPointer<vtkAxesActor> actor2 = 	vtkSmartPointer<vtkAxesActor>::New();
actor2->SetPosition(0, 0, 0);
actor2->SetTotalLength(2,2,2);
actor2->SetShaftType(0);
actor2->SetAxisLabels(0);
actor2->SetCylinderRadius(0.02);
renderer->AddActor(actor2);

renderer->SetBackground(0.1,0.2,0.4);
renderer->ResetCamera();

this->qvtkWidget->GetRenderWindow()->AddRenderer(renderer);

}

Thank you for your help

Leo

2

After bulk operations on an array, you need to indicate that you have finished the updates by calling its Modified() method.

3

Andras Lasso, Thanks for your quickly reply, I have tried adding da->Modified() aft da->SetArray(temperature,8,1), but it not work yet.

4

I don’t have any other idea, but you can easily see what goes wrong if you go execute your code in a debugger - stepping into VTK methods, to see if they do what you expect.

5

Hi, friend,

I think you need to set a transfer function for your LUT object. I set my color mapping with this:

vtkSmartPointer<vtkLookupTable> getClassicRainbow(double min, double max)
{
    size_t tableSize = 32;

    //create a color interpolator object
    vtkSmartPointer<vtkColorTransferFunction> ctf =
            vtkSmartPointer<vtkColorTransferFunction>::New();
    ctf->SetColorSpaceToRGB();
    ctf->AddRGBPoint(0.00, 0.000, 0.000, 1.000);
    ctf->AddRGBPoint(0.25, 0.000, 1.000, 1.000);
    ctf->AddRGBPoint(0.50, 0.000, 1.000, 0.000);
    ctf->AddRGBPoint(0.75, 1.000, 1.000, 0.000);
    ctf->AddRGBPoint(1.00, 1.000, 0.000, 0.000);

    //create the color table object
    vtkSmartPointer<vtkLookupTable> lut = vtkSmartPointer<vtkLookupTable>::New();
    lut->SetTableRange(min, max);
    lut->SetNumberOfTableValues(tableSize);
    for(size_t i = 0; i < tableSize; ++i)
    {
        double *rgb;
        rgb = ctf->GetColor(static_cast<double>(i)/tableSize);
        lut->SetTableValue(i, rgb[0], rgb[1], rgb[2]);
    }
    lut->SetRampToLinear();
    lut->Build();

    return lut;
}

I hope this helps,

Paulo

6

Paulo, Thank you for suggestion ， But maybe it is not the problem, because I have tried the commentted codes replace the SetArray():
// for(int i=0;i<8;i++)
// da->InsertNextTuple1(temperature[i]); //Method 2： using InsertNextTuple() add temperature 1 by 1 is effective.

it works well,the result color is mapping successfully， so I think the problem is logically I input temperature array at once using SetArray（）， actually it is not completed， I miss some key commands，but I don’t know which is missed， There are few detailed VTk documents online and it is difficult to find relevant examplest。

7

Ok… I just do like you: I set the values array at once, but I use unstructuredGrid->GetCellData()->SetScalars( values ); instead. I never used SetArray(). You can take a look at how I use it to assign values to the different VTK data structures here (search for SetScalars): https://github.com/PauloCarvalhoRJ/gammaray/blob/master/viewer3d/view3dbuilders.cpp .

I hope this cast light onto your problem.

regards,

Paulo

8

Hi, Paulo Carvalho,Thank you for your patient reply,however I already used the setscalars(), please see the following code snip:
ug->GetPointData()->SetScalars(da);
qDebug()<GetPointData()->GetArrayName(0);
ug->GetPointData()->SetActiveScalars(“temp”);

because SetScalars()'s parameter is vtkDoubleArray, before you use SetScalars(), you have to fill the vtkDoubleArray, one method is insert 1 by 1, the other is fill all value at once using SetArray(),The former is more robust and work well， but I think the latter is more efficiency, now the problem is I can not make it work good?

In your example , you use the former method , not use SetArray() method.
image

anyway, thank you all the same!

9

Well, SetScalars() works just fine for me. No 1 by 1 here. I don’t use SetArray() in any of my numerous VTK pipelines. If you want to stick to SetArray() then I can’t help you, sorry. Good luck.

10

Ah… I see what you need. But, anyway, I don’t have any code ready by now using SetArray(). Sorry.

11

In such cases, the easiest is to step through the code using a debugger - stepping into VTK methods, too. It makes it obvious what happens, why, and what needs to be changed in your code or fixed/documented better in VTK.