vtkMultiBlockDataSet can not show vtkUnstructuredGrid data?

Support
1

When I input a vtkUnstructuredGrid data into vtkMultiBlockDataSet, it can not show the data.
Does the vtkMultiBlockDataSet only can show vtkPolyData?

vtkNew<vtkMultiBlockDataSet> root;

vtkNew<vtkSphereSource> block1;
block1->SetCenter(0, 0, 0);
block1->SetRadius(2);
block1->Update();

vtkNew<vtkSphereSource> block2;
block2->SetCenter(10, 10, 10);
block2->SetRadius(5);
block2->Update();

// Combine the two data sets
vtkSmartPointer<vtkAppendFilter> appendFilter =
    vtkSmartPointer<vtkAppendFilter>::New();
appendFilter->AddInputData(block1->GetOutput());
appendFilter->AddInputData(block2->GetOutput());
appendFilter->Update();

vtkSmartPointer<vtkUnstructuredGrid> unstructuredGrid =
    vtkSmartPointer<vtkUnstructuredGrid>::New();
unstructuredGrid->ShallowCopy(appendFilter->GetOutput());

root->SetBlock(0, unstructuredGrid);

// root->SetBlock(1, block2->GetOutput());
vtkNew mapper;
mapper->SetInputDataObject(root);

2

I don’t see a call to vtkMultiBlockDataSet::SetNumberOfBlocks(1), which you probably need here.

3

Actually, I take that back. Resizing should be taken care of automatically.

4

Thanks. However, it still not work even I add vtkMultiBlockDataSet::SetNumberOfBlocks(1).
I found the block number can increase automatically if insert a new dataset.