# First release of fVTKHDF: A modern Fortran library for writing VTKHDF files
**URL:** https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304
**Category:** Support
**Tags:** file-formats
**Created:** [February 25, 2026, 4:35am UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304 "2026-02-25T04:35:11Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@nncarlson](https://discourse.vtk.org/u/nncarlson)
#### Post date: [February 25, 2026, 4:35am UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/1 "2026-02-25T04:35:11Z")
If you’re a Fortran’er, this may be of interest to you.
I’ve just published the first release of [fVTKHDF](https://github.com/nncarlson/fvtkhdf), a high-level, object-oriented Fortran library for writing VTKHDF files.
It currently supports UnstructuredGrid (UG) and MultiBlockDataSet (MB) types of VTK datasets with temporal data – the itch I needed to scratch. The MB dataset is limited to a flat assembly of UG blocks (no hierarchical nesting of MB), so it’s essentially equivalent in this form to a PartitionedDataSetCollection.
The library is fully parallel, using parallel HDF5 (MPI-IO) for collective writes to partitioned datasets.
See the [Github project page](https://github.com/nncarlson/fvtkhdf) for more information and the Reference Manual.
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [February 25, 2026, 8:35am UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/2 "2026-02-25T08:35:11Z")
This is glorious @nncarlson ! Thanks a lot!
In your readme you mention:
> ParaView 5.13+ recommended for full support of the generated files.
I would recommend 6.0 (or even 6.1!) to get the last improvements that have been added to the format 🙂
Any specific reason to not support PDC, it should be pretty similar to MB ?
@lgivord @Louis_Gombert
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### Author:  [@nncarlson](https://discourse.vtk.org/u/nncarlson)
#### Post date: [February 25, 2026, 1:41pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/3 "2026-02-25T13:41:00Z")
> Any specific reason to not support PDC, it should be pretty similar to MB ?
In fact for my “flat” Assembly of leaf nodes it is identical; I only needed to assign a different value to the `Type` attribute. My sole reason for reverting to MB was because of this [bug](https://gitlab.kitware.com/vtk/vtk/-/issues/19902#note_1754723). It was fixed very recently, but I don’t think it made it into 9.6. My plan is to shift to PDC as soon as the fix is available in ParaView.
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [February 25, 2026, 1:51pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/4 "2026-02-25T13:51:07Z")
> [@nncarlson](#):
>
> but I don’t think it made it into 9.6.
Correct
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### Author:  [@lgivord](https://discourse.vtk.org/u/lgivord)
#### Post date: [February 25, 2026, 1:59pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/5 "2026-02-25T13:59:39Z")
we should probably backport it in release in case we plan to do a 9.6.1, it’s an important bug fix imo
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [February 25, 2026, 2:57pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/6 "2026-02-25T14:57:46Z")
Agreed
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [March 2, 2026, 12:43pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/7 "2026-03-02T12:43:45Z")
Backport is here: [https://gitlab.kitware.com/vtk/vtk/-/merge\_requests/12972](https://gitlab.kitware.com/vtk/vtk/-/merge_requests/12972)
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### Author:  [@nncarlson](https://discourse.vtk.org/u/nncarlson)
#### Post date: [March 2, 2026, 1:35pm UTC](https://discourse.vtk.org/t/first-release-of-fvtkhdf-a-modern-fortran-library-for-writing-vtkhdf-files/16304/8 "2026-03-02T13:35:48Z")
Excellent. Thanks!