# Creating a simple polyline VTKHDF
**URL:** https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828
**Category:** Support
**Created:** [May 1, 2024, 5:29pm UTC](https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828 "2024-05-01T17:29:53Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@Nikolaos\_Beratlis](https://discourse.vtk.org/u/Nikolaos_Beratlis)
#### Post date: [May 1, 2024, 5:29pm UTC](https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828/1 "2024-05-01T17:29:53Z")
I have created a simple legacy VTK for a bunch of lines as shown below:
```auto
# vtk DataFile Version 3.0
vtk output
ASCII
DATASET POLYDATA
POINTS 4 float
0 0 0
1 1 0
1 2 0
2 0 0
LINES 2 8
3 0 1 3
3 4 2 0
```
I want to create the same geometry in VTKHDF (using Fortran code). I read through the example “test\_poly\_data.hdf” but i am confused as to when to create a group or a dataset or an attribute, some datasets in the example are within some groups and other datasets don’t belong to any group. So far I was able to create the header of VTKHDF
```auto
HDF5 "file.hdf" {
GROUP "/" {
GROUP "VTKHDF" {
ATTRIBUTE "Type" {
DATATYPE H5T_STRING {
STRSIZE 9;
STRPAD H5T_STR_NULLTERM;
CSET H5T_CSET_ASCII;
CTYPE H5T_C_S1;
}
DATASPACE SCALAR
DATA {
(0): "PolyData"
}
}
ATTRIBUTE "Version" {
DATATYPE H5T_STD_I32LE
DATASPACE SIMPLE { ( 2 ) / ( 2 ) }
DATA {
(0): 2, 2
}
}
}
}
}
```
Do I need to create a stand alone dataset called “Points” next? How do I create the lines?
---
### Author:  [@Nikolaos\_Beratlis](https://discourse.vtk.org/u/Nikolaos_Beratlis)
#### Post date: [May 1, 2024, 6:53pm UTC](https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828/2 "2024-05-01T18:53:43Z")
I created the following hdf5 file:
```auto
HDF5 "file.hdf" {
GROUP "/" {
DATASET "LINES" {
DATATYPE H5T_STD_I32LE
DATASPACE SIMPLE { ( 2, 2 ) / ( 2, 2 ) }
DATA {
(0,0): 1, 3,
(1,0): 2, 4
}
}
DATASET "POINTS" {
DATATYPE H5T_IEEE_F32LE
DATASPACE SIMPLE { ( 4, 3 ) / ( 4, 3 ) }
DATA {
(0,0): 1.2, 4.5, 1,
(1,0): 6, 2.3, 5,
(2,0): 8, 5, 3.4,
(3,0): 6, 9, 3
}
}
GROUP "VTKHDF" {
ATTRIBUTE "Type" {
DATATYPE H5T_STRING {
STRSIZE 9;
STRPAD H5T_STR_NULLTERM;
CSET H5T_CSET_ASCII;
CTYPE H5T_C_S1;
}
DATASPACE SCALAR
DATA {
(0): "PolyData"
}
}
ATTRIBUTE "Version" {
DATATYPE H5T_STD_I32LE
DATASPACE SIMPLE { ( 2 ) / ( 2 ) }
DATA {
(0): 2, 2
}
}
}
}
}
```
It contains a dataset named “POINTS” and another one named “LINES” similar to the legacy VTK file. But Paraview 5.12.0 can’t read it. A pop-up window appears called “Open Data Wtih…” with the default option ADIOS2VTXReader. I click OK and Paraview crashes.
---
### Author:  [@geoffw](https://discourse.vtk.org/u/geoffw)
#### Post date: [May 2, 2024, 7:38pm UTC](https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828/3 "2024-05-02T19:38:28Z")
Can you find an example of the file that loads successfully and just compare the formats?
---
### Author:  [@lgivord](https://discourse.vtk.org/u/lgivord)
#### Post date: [May 3, 2024, 6:19am UTC](https://discourse.vtk.org/t/creating-a-simple-polyline-vtkhdf/13828/4 "2024-05-03T06:19:18Z")
Hello @Nikolaos_Beratlis,
There is complete documentation about the file format which explain what you’ll need to create in term of groups, datasets and attributes here: [VTK File Formats - VTK documentation](https://docs.vtk.org/en/latest/design_documents/VTKFileFormats.html#poly-data)
You can also check this repository which contains several python scripts to generate valid vtkhdf file, sadly the script for polydata is a bit complex but it can help you: [https://gitlab.kitware.com/keu-public/vtkhdf/vtkhdf-scripts](https://gitlab.kitware.com/keu-public/vtkhdf/vtkhdf-scripts)