# vtkMultiBlockDataSet can not show vtkUnstructuredGrid data?

**URL:** https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456
**Category:** Support
**Created:** [September 26, 2022, 5:38am UTC](https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456 "2022-09-26T05:38:17Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![rockydut](https://discourse.vtk.org/user_avatar/discourse.vtk.org/rockydut/32/4261_2.png) [@rockydut](https://discourse.vtk.org/u/rockydut)
#### Post date: [September 26, 2022, 5:38am UTC](https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456/1 "2022-09-26T05:38:17Z")

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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);

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<div class="post-metadata">

### Author: ![cory.quammen](https://discourse.vtk.org/user_avatar/discourse.vtk.org/cory.quammen/32/6751_2.png) [@cory.quammen](https://discourse.vtk.org/u/cory.quammen)
#### Post date: [September 26, 2022, 9:41pm UTC](https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456/2 "2022-09-26T21:41:17Z")

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

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<div class="post-metadata">

### Author: ![cory.quammen](https://discourse.vtk.org/user_avatar/discourse.vtk.org/cory.quammen/32/6751_2.png) [@cory.quammen](https://discourse.vtk.org/u/cory.quammen)
#### Post date: [September 26, 2022, 9:43pm UTC](https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456/3 "2022-09-26T21:43:02Z")

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

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<div class="post-metadata">

### Author: ![rockydut](https://discourse.vtk.org/user_avatar/discourse.vtk.org/rockydut/32/4261_2.png) [@rockydut](https://discourse.vtk.org/u/rockydut)
#### Post date: [September 26, 2022, 11:57pm UTC](https://discourse.vtk.org/t/vtkmultiblockdataset-can-not-show-vtkunstructuredgrid-data/9456/4 "2022-09-26T23:57:55Z")

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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.