OFF#

.off read + write eager

Summary of the specification#

The Object File Format opens with an OFF magic line, optionally prefixed by variant letters, then a counts line giving the number of vertices, faces and edges (the edge count is conventionally ignored). Vertex coordinates follow one per line, then one line per face: a vertex count followed by that many 0-based indices, optionally trailed by per-face colour components. The ST, C, N and 4 prefixes declare that vertices additionally carry texture coordinates, colour, normals or a fourth homogeneous component, in that fixed order.

Specification at a glance#

magic	[ST][C][N][4][n]OFF, optionally followed by BINARY
counts line	nvertices nfaces nedges (edges ignored)
faces	<k> i0 i1 … ik-1, 0-based, optional trailing colour
variants	ST = texture coords, C = colour, N = normals, 4 = homogeneous
binary form	big-endian, IEEE floats and 32-bit ints

Read the full OFF specification ↗

Reading#

import polyxios as px

mesh = px.read("model.off")
mesh.vertices          # (n, 3)
mesh.element_types     # one type code per element

Writing#

px.write(mesh, "out.off")
px.write(mesh, "out.off", binary=True)

Format-specific options#

Option	Default	Effect
`binary`	`False`	Write big-endian binary OFF (`OFF BINARY`) instead of ASCII.
`float_fmt`	`".10g"`	ASCII coordinate format specifier; pass `".17g"` for a bit-exact round trip.

Quirks worth knowing#

ASCII and big-endian binary OFF are both read and written; writing emits ASCII unless binary=True.
ST / C / N variant data is mapped onto vertex_attrs (texcoords, colors, normals) and per-face colours onto element_attrs['colors'] instead of being discarded.
4OFF and an nOFF of a dimension other than three are refused with CodecError rather than flattened to 3-D.
The edge count on the counts line is ignored, as the format intends - no error is raised when it disagrees with the face list.