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VTK (file format)

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VTK (file format)
NameVTK (file format)
Extension.vtk, .vtp, .vti, .vtr, .vts, .vtu, .pvtk, .pvti, .pvd
DeveloperKitware
Released1993
GenreScientific data file format
WebsiteKitware

VTK (file format) is a legacy and modern file format family associated with the Visualization Toolkit project and maintained by Kitware. It is used for storing and exchanging three-dimensional data for visualization and analysis in contexts such as computational fluid dynamics, finite element analysis, medical imaging, and geoscience. The format family interoperates with software ecosystems including ParaView, MayaVi, VTK (software), and scientific libraries across platforms such as Linux, Windows, and macOS.

Introduction

The VTK file family originated within the Visualization Toolkit initiative led by contributors connected to institutions like Los Alamos National Laboratory and commercial entities such as Kitware. It was designed to represent structured and unstructured meshes, polygonal models, and image data for workflows that involve tools like ParaView and MayaVi and research groups at organizations including Sandia National Laboratories, Argonne National Laboratory, Lawrence Livermore National Laboratory, and universities such as Stanford University and Massachusetts Institute of Technology. The format supports both human-readable and binary encodings to serve developers and high-performance computing projects at centers like Oak Ridge National Laboratory and CERN.

File Formats and Variants

The VTK family comprises multiple file types: legacy ASCII/binary .vtk files and XML-based formats with extensions such as .vtu, .vtp, .vts, .vtr, .vti, and parallel variants .pvtu, .pvtp, .pvts, .pvtr, .pvti. These variants map to data models used across projects including ParaView, VisIt, MayaVi, OpenFOAM, and visualization libraries maintained by Kitware and contributors at institutions like Lawrence Berkeley National Laboratory. XML variants were introduced to improve metadata expressiveness and parallel IO interoperability important to initiatives at DOE laboratories and academic consortia like SciDAC.

Data Model and Structure

VTK formats encode a hierarchical data model covering dataset types such as UnstructuredGrid, PolyData, RectilinearGrid, StructuredPoints, StructuredGrid, and ImageData. This model mirrors concepts used in mesh-centric projects at organizations including NASA, NOAA, USGS, Siemens, and academic centers like ETH Zurich and Imperial College London. Files represent topology and geometry separately: point coordinates, cell connectivity, and attribute arrays (point data, cell data) similar to representations used in finite element codes at CEA and EPFL laboratories. Metadata tags in XML variants enable integration with workflows from institutions like NCAR, JPL, MIT, and companies such as Intel and NVIDIA that optimize IO and memory layouts.

Supported Data Types and Cells

VTK supports scalar, vector, tensor, and matrix attribute arrays with numeric types including float, double, int, and unsigned variants; these types are compatible with processing pipelines at LLNL, Sandia, and academic groups at Carnegie Mellon University. Cell types include vertices, lines, polygons, triangle strips, and higher-order elements such as tetrahedra, hexahedra, pyramids, and wedges—cell vocabularies used by finite element and CFD codes at ANSYS, COMSOL, OpenFOAM, and research groups at Caltech and Princeton University.

File Encoding and Compression

Legacy .vtk supports ASCII and raw binary encodings; XML-based files allow Base64 encoding and raw binary data blocks. Compression options include built-in zlib compression (gzip) layers combined with XML structure, matching IO strategies used in high-performance computing centers like Argonne National Laboratory and projects optimized for MPI-based parallel IO at NERSC and Oak Ridge National Laboratory. Parallel variants (.pvtu/.pvts, etc.) coordinate piecewise datasets with master metadata to support distributed visualization in environments used by EuroHPC and national supercomputing centers.

Usage and Software Support

Software supporting VTK formats spans visualization packages such as ParaView, VisIt, MayaVi, and the VTK library itself, and extends to modeling and simulation tools like OpenFOAM, Blender (via exporters), ANSYS, and custom workflows in Python with bindings from projects like NumPy, SciPy, pandas, and h5py when converting between formats. Integration with scientific ecosystems at universities and labs enables use in pipelines developed at UC Berkeley, University of Cambridge, ETH Zurich, and Harvard University and commercial analytics stacks from Microsoft and Amazon Web Services when visualizing results at scale.

Examples and File Syntax

Examples commonly include a legacy ASCII .vtk for PolyData and XML snippets for .vtu UnstructuredGrid. Typical legacy files declare header, dataset type, points block, cells block, and data attributes; XML examples use and elements with DataArray children and optional AppendedData sections. Conversion utilities exist in VTK (software), ParaView, and community tools maintained by Kitware contributors and research groups at UCSF and University of Illinois Urbana-Champaign.

Category:File formats