# Improve FieldData in vtkHDF temporal format

**URL:** https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669
**Category:** Development
**Tags:** file-formats, proposal
**Created:** [April 4, 2024, 9:14am UTC](https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669 "2024-04-04T09:14:08Z")
**Posts on this page:** 4
**Page:** 1

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### Author: ![Timothee\_Couble](https://discourse.vtk.org/user_avatar/discourse.vtk.org/timothee_couble/32/3086_2.png) [@Timothee\_Couble](https://discourse.vtk.org/u/Timothee_Couble)
#### Post date: [April 4, 2024, 9:14am UTC](https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669/1 "2024-04-04T09:14:08Z")

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Hello,

Currently, the temporal (transient) vtkHDF file does not fully support field data with multiple components and tuples. Only the first tuple with all its components is read.

The main issue is that the number of components and tuples can change from one step to another, so we need a way to know their size for each step.

Here is a proposal to add a new group in the [hdf format](https://docs.vtk.org/en/latest/design_documents/VTKFileFormats.html#transient-data) `Steps/FieldDataSize`. In this group, each field data could have a dataset representing the component and tuple size. For example:

For a field data dataset named `FieldData/MyField` (with 2 steps):   
 ![image](https://discourse.vtk.org/uploads/default/original/2X/6/6b32142d9ff158b8d384ddb13c73e28a0c11ebdb.png)

It should have offsets `Steps/FieldDataOffsets/MyField`:   
 ![image](https://discourse.vtk.org/uploads/default/original/2X/c/ce21261a55b2bd7456f09efc1a6154d67148e7c2.png)

And a new dataset specifying its size, `Steps/FieldDataSize/MyField`, with the first column representing component size and the second column representing tuple size:   
 ![image](https://discourse.vtk.org/uploads/default/original/2X/4/40ee2aa622570da9ddee98f23bf4a7c6e310a184.png)

Any comments or suggestions are welcome!

Thanks,

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<div class="post-metadata">

### Author: ![Timothee\_Couble](https://discourse.vtk.org/user_avatar/discourse.vtk.org/timothee_couble/32/3086_2.png) [@Timothee\_Couble](https://discourse.vtk.org/u/Timothee_Couble)
#### Post date: [April 4, 2024, 9:14am UTC](https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669/2 "2024-04-04T09:14:29Z")

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FYI @mwestphal @lgivord

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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: [April 4, 2024, 10:28am UTC](https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669/3 "2024-04-04T10:28:31Z")

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FYI @hakostra

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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: [April 26, 2024, 1:06pm UTC](https://discourse.vtk.org/t/improve-fielddata-in-vtkhdf-temporal-format/13669/4 "2024-04-26T13:06:27Z")

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Implemented here: [https://gitlab.kitware.com/vtk/vtk/-/merge\_requests/11067](https://gitlab.kitware.com/vtk/vtk/-/merge_requests/11067)