# MultiBlockDataSet field data inaccessible from outer layer

**URL:** https://discourse.vtk.org/t/multiblockdataset-field-data-inaccessible-from-outer-layer/482
**Category:** Development
**Created:** [March 13, 2019, 8:14pm UTC](https://discourse.vtk.org/t/multiblockdataset-field-data-inaccessible-from-outer-layer/482 "2019-03-13T20:14:20Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![phil\_ossk](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/p/858c86/32.png) [@phil\_ossk](https://discourse.vtk.org/u/phil_ossk)
#### Post date: [March 13, 2019, 8:14pm UTC](https://discourse.vtk.org/t/multiblockdataset-field-data-inaccessible-from-outer-layer/482/1 "2019-03-13T20:14:20Z")

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Hello there,

Before submitting a bug report, I am looking for your input on an issue I am facing.

I have a MultiBlockDataSet (let’s call it **mbds0** ) with several blocks . Some field data ( **testArray0** and **testArray1** ) has been appended to it, but it is not part of any block. At this stage I can access that data just fine.

 ![1](https://discourse.vtk.org/uploads/default/original/1X/30837461d4da09ceab728d6f27c3deec0abf3eba.png)

> print mbds0.GetFieldData().GetNumberOfArrays()

outputs _2_ as expected.

* * *

* * *

Now, let’s say that I need to set **mbds0** as the first block of a larger MultiBlockDataSet (that we’ll call **mbds1** ) like so:

 ![2](https://discourse.vtk.org/uploads/default/original/1X/31a0823bffde3ba8f0b31aeca075c6c6b07aee1f.png)

I can see the arrays in ParaView but I can’t access them at all.

> print mbds1.GetBlock(0).GetFieldData().GetNumberOfArrays()

outputs 0.  
I can’t manage to access my field data.

* * *

* * *

Here’s how to reproduce it, since I can’t upload my pvsm.

Programmable Source ( **mbds0** )

> import vtk
> 
> output = self.GetOutputDataObject(0)
> 
> strarray0 = vtk.vtkStringArray()  
> strarray0.SetName(‘testArray0’)  
> strarray0.InsertNextValue(‘testVal0’)  
> strarray0.InsertNextValue(‘testVal1’)
> 
> strarray1 = vtk.vtkStringArray()  
> strarray1.SetName(‘testArray1’)  
> strarray1.InsertNextValue(‘testVal2’)  
> strarray1.InsertNextValue(‘testVal3’)
> 
> pd0 = vtk.vtkPolyData()  
> pd1 = vtk.vtkPolyData()  
> mbds0 = vtk.vtkMultiBlockDataSet()  
> mbds0.SetBlock(0, pd0)  
> mbds0.SetBlock(1, pd1)  
> mbds0.GetFieldData().AddArray(strarray0)  
> mbds0.GetFieldData().AddArray(strarray1)
> 
> output.DeepCopy(mbds0)

Programmable filter to wrap **mbds0** in **mbds1**

> import vtk
> 
> input = self.GetInputDataObject(0, 0)  
> output = self.GetOutputDataObject(0)
> 
> mbds1 = vtk.vtkMultiBlockDataSet()  
> mbds1.SetBlock(0, input)
> 
> output.DeepCopy(mbds1)

Also tried using PassData but still no luck.

* * *

* * *

Finally, extracting **mdbs0** from **mdbs1** results in the Field Data being gone completely and not showing in ParaView at all.

> import vtk
> 
> input = self.GetInputDataObject(0, 0)  
> output = self.GetOutputDataObject(0)
> 
> output.DeepCopy(input.GetBlock(0))

Thanks a lot 🙂

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### Author: ![mwestphal](https://discourse.vtk.org/user_avatar/discourse.vtk.org/mwestphal/32/19_2.png) [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [March 14, 2019, 9:22am UTC](https://discourse.vtk.org/t/multiblockdataset-field-data-inaccessible-from-outer-layer/482/2 "2019-03-14T09:22:34Z")

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Afaik, Field Data should be added on the leaf block.

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<div class="post-metadata">

### Author: ![phil\_ossk](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/p/858c86/32.png) [@phil\_ossk](https://discourse.vtk.org/u/phil_ossk)
#### Post date: [March 14, 2019, 1:51pm UTC](https://discourse.vtk.org/t/multiblockdataset-field-data-inaccessible-from-outer-layer/482/3 "2019-03-14T13:51:44Z")

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Thank you Mathieu, I’ll do that.

Is it worth reporting?