VTK Legacy#

.vtk read + write lazy: binary only

Summary of the specification#

The legacy VTK format is a single-dataset serial file with a five-line ASCII preamble — version banner, title, ASCII or BINARY data mode, and a DATASET keyword naming the geometry type. What follows depends on that type: an unstructured grid lists POINTS, then CELLS as connectivity lists prefixed by their point count, then a parallel CELL_TYPES array of integer type codes. Point and cell attributes arrive afterwards in POINT_DATA / CELL_DATA sections as named SCALARS, VECTORS or FIELD arrays. In BINARY mode the arrays are raw big-endian values packed straight after their declaration line.

Specification at a glance#

banner	# vtk DataFile Version x.y
data mode	ASCII or BINARY (binary payload is big-endian)
dataset types	STRUCTURED_POINTS, STRUCTURED_GRID, RECTILINEAR_GRID, POLYDATA, UNSTRUCTURED_GRID
connectivity	CELLS <n> <size> followed by CELL_TYPES <n> integer codes
attributes	POINT_DATA / CELL_DATA with SCALARS, VECTORS, NORMALS, FIELD

Read the full VTK Legacy specification ↗

Reading#

import polyxios as px

mesh = px.read("model.vtk")
mesh.vertices          # (n, 3)
mesh.element_types     # element groups found in the file

Binary bodies can be memory-mapped instead of loaded:

mesh = px.read("big.vtk", lazy=True)

Writing#

px.write(mesh, "out.vtk")

Format-specific options:

Option	Default	Effect
`binary`	`False`	Write a BINARY body instead of ASCII.

Quirks worth knowing#

Binary files can be memory-mapped with lazy=True; ASCII files must be parsed end to end before any value is available.
Cell type codes are mapped to polyxios element types, so a file mixing triangles, quads and tetrahedra keeps every group separate.
Point and cell data arrays are carried through as named vertex and element attributes rather than being dropped on read.