Well-Known Text#

.wkt read + write eager

Summary of the specification#

WKT is the OGC text encoding for vector geometry: a type keyword followed by parenthesised coordinate lists. POLYGON takes one or more rings, the first being the exterior boundary and the rest holes; MULTIPOLYGON nests one level deeper; TRIANGLE, POLYHEDRALSURFACE and TIN describe surfaces directly. Coordinates are whitespace-separated within a tuple and comma-separated between tuples. The EWKT extension prefixes a spatial reference as SRID=4326;, and Z / M suffixes declare extra ordinates.

Specification at a glance#

geometry types	POINT, LINESTRING, POLYGON, MULTI*, TRIANGLE, TIN, POLYHEDRALSURFACE
polygon rings	first ring exterior, subsequent rings are holes
coordinates	x y [z [m]], space-separated in a tuple, comma-separated between
dimensions	Z / M / ZM suffixes on the type keyword
EWKT	optional SRID=<n>; prefix

Read the full Well-Known Text specification ↗

Reading#

import polyxios as px

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

Writing#

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

This codec takes no format-specific options.

Quirks worth knowing#

A 2-D file’s coordinates are padded with a zero z, so the mesh is 3-D like every other one polyxios holds, and global_attrs["was_2d"] records the fact. The Z suffix follows it. The writer puts it back so long as the vertices have stayed in the plane; a mesh whose vertices have since left it is written in three with a warning.
Interior rings are preserved as element attributes rather than being merged into the exterior boundary or dropped.
An EWKT SRID= prefix is parsed and then dropped - polyxios carries no coordinate reference system.
The ISO/SQL-MM surface family reads too: TRIANGLE as one triangle, TIN as a set of them, POLYHEDRALSURFACE as a set of polygons. A TIN patch that is not a triangle, or a TRIANGLE carrying an interior ring, is refused rather than read as something else.
EMPTY is a legal geometry for every type, including the surface family, and parses to an empty mesh rather than an error.
lazy=True raises LazyReadError; the geometry is spelled as text and has to be parsed before it holds numbers.