Struggling to create a simple (legacy) unstructured mesh with just 1 triangle cell

Dear All,

As the title tells, I’m struggling to create a simple (legacy) unstructured mesh with just 1 triangle cell at the origin.
I’m opening the file with paraview 5.9.1 and keep getting unrecognized keyword.

I’ve read info on vtk unstr file https://examples.vtk.org/site/VTKFileFormats/#dataset-format

Here the mesh :

 # vtk DataFile Version 2.0
 Unstructured Grid Example
 ASCII
 DATASET UNSTRUCTURED_GRID
 POINTS 3 float
 0.0 0.0 0.0
 1.0 0.0 0.0
 0.5 0.5 0.0
 CELLS 1 3
 0 1 2
 CELL_TYPES 1
 5

Thank you very much for your help

Paraview these days uses vtk DataFile Version 5.1. Unfortunately, however, there appears to be no formal documentation on this yet.
https://gitlab.kitware.com/vtk/vtk/-/issues/17989

Therefore, if you are applying Version 5.1 to your own data, you will need to output similar data from ParaView in ASCII format and decipher it.

In this example, you would need to do the following.

# vtk DataFile Version 5.1
 Unstructured Grid Example
 ASCII
 DATASET UNSTRUCTURED_GRID
 POINTS 3 float
 0.0 0.0 0.0
 1.0 0.0 0.0
 0.5 0.5 0.0
 CELLS 2 3
 OFFSETS vtktypeint64
 0 3 
 CONNECTIVITY vtktypeint64
 0 1 2 
 CELL_TYPES 1
 5