VTKHDF.jl

Write and read VTK data in the VTKHDF file format, the HDF5-based successor to the VTK XML formats, readable by ParaView, VisIt and VTK. The writing API follows WriteVTK.jl and shares its cell and data-location types through VTKBase.jl. vtkhdf_open reads those files back into Julia, including spec-conforming VTKHDF files from other writers.

Time series can live in a single file: for a transient simulation on a fixed mesh the geometry is stored once, and each time step appends only its data arrays, instead of a .pvd collection with one .vtu file per step.

using VTKHDF

points = [                 # unit cube; vectors of SVector/tuples also work
    0.0 1.0 1.0 0.0 0.0 1.0 1.0 0.0
    0.0 0.0 1.0 1.0 0.0 0.0 1.0 1.0
    0.0 0.0 0.0 0.0 1.0 1.0 1.0 1.0
]
cells = [MeshCell(VTKCellTypes.VTK_HEXAHEDRON, 1:8)]

# static file
vtkhdf_grid("output", points, cells) do vtk
    vtk["height"] = points[3, :]             # point data (auto-detected)
    vtk["material", VTKCellData()] = [1]
    vtk["position", VTKPointData(), attribute = :Vectors] = points
end

# temporal file — geometry written once, data appended per step
timesteps = 0.0:0.1:1.0
vtk = vtkhdf_grid("simulation", points, cells; temporal = true)
for t in timesteps
    write_timestep(vtk, t) do frame
        frame["u"] = fill(t, 8)
    end
end
close(vtk)

# reading files back
vtkhdf_open("output") do r
    height = r["height"]                      # same indexing as writing
    points, cells = read_points(r), read_cells(r)
end
vtkhdf_open("simulation") do r
    step = read_timestep(r, VTKHDF.nsteps(r))
    u_end = step["u"]
end

Supported dataset types

VTKHDF type	write	read	temporal
UnstructuredGrid (incl. polyhedra, multiple partitions)	✓	✓	✓
PolyData (vertices/lines/polygons/strips)	✓	✓	✓
ImageData	✓	✓	✓
RectilinearGrid	✓	✓	✓
StructuredGrid	✓	✓	✓
Table	✓	✓	✓
OverlappingAMR	✓	✓	–
HyperTreeGrid	✓	✓	–
PartitionedDataSetCollection / MultiBlockDataSet	✓	✓	✓

Plus gzip compression (compress = true), active attribute marking (Scalars/Vectors/...), and writing datasets as blocks of composite files. Files are validated against VTK's own vtkHDFReader in the test suite.

See the documentation for the full manual.

Development

This package was mainly developed with AI assistance (Claude Code), guided by the VTKHDF specification, with the file format output validated against the VTK reference implementation.