Working with VTK Files

The Visualization Toolkit (VTK) establishes a data format which is designed for use in high performance computing (HPC) applications. Detailed documentation of data format can be found on the website at VTK File Formats. This page provides a high level summary of the data format and a quick start guide to working with VTK files generated by FDS.

Data format

The VTK framework uses separate files and pointers to organize the data. The pointer files are small and contain the information required by the visualization to identify which files have sections of data. This allows individual computing processes to identify which files are needed to fulfill a data request by the software without having to read the files containing the data. By convention, the pointer files (or parallel file formats) include the letter p at the front of the extension (e.g., pvtu indicates a parallel vtu file). An example pvtu file for boundary data is shown below.

<?xml version="1.0"?>
<VTKFile type="PUnstructuredGrid" version="1.0" byte_order="LittleEndian">
<PUnstructuredGrid GhostLevel="0">
<PPoints>
<PDataArray type="Float32" NumberOfComponents="3" NAME="POINTS"/>
</PPoints>
<PPointData>
<PDataArray type="Float32" Name="water drops AMPUA" NumberOfComponents="1"/>
<PDataArray type="Float32" Name="WALL TEMPERATURE" NumberOfComponents="1"/>
<PDataArray type="Float32" Name="HRRPUA" NumberOfComponents="1"/>
</PPointData>
<PCellData>
</PCellData>
<Piece Source="storage_BNDF_1_0000000112.vtu"/>
<Piece Source="storage_BNDF_2_0000000112.vtu"/>
<Piece Source="storage_BNDF_3_0000000112.vtu"/>
<Piece Source="storage_BNDF_4_0000000112.vtu"/>
<Piece Source="storage_BNDF_5_0000000112.vtu"/>
<Piece Source="storage_BNDF_6_0000000112.vtu"/>
<Piece Source="storage_BNDF_7_0000000112.vtu"/>
<Piece Source="storage_BNDF_8_0000000112.vtu"/>
</PUnstructuredGrid>
</VTKFile>

The example shows a parallel VTK file for boundary data. Each block contains a pointer to the type of data stored within the individual pieces linked at the bottom of the file. The data files contain three quantities "water drops AMPUA", "WALL TEMPERATURE", and "HRRPUA" stored at the nodes (indicated by the definition within the <PPointData> block) and no data stored at the cell-centers (indicated by the blank <PCellData> block). FDS outputs a separate piece for each mesh at each time step.

The individual data files store the data output by FDS. For a detailed discussion of how the data is stored, see the VTK File Formats.

Paraview State File