WKT / TIN (.wkt)

The Well-Known Text representation of a Triangulated Irregular Network: TIN (((x y z, x y z, x y z, x y z)), …) — one closed 4-point ring per triangle (the 4th point repeats the 1st, closing the ring).

Format name	wkt
Extensions	.wkt
Read / Write	✓ / ✓
Extra dependencies	—

Reading & writing

import meshioplusplus

mesh = meshioplusplus.read("surface.wkt")
meshioplusplus.wkt.write("out.wkt", mesh)

write takes no keyword arguments.

File structure

A single TIN (...) expression. Each triangle is ((p0, p1, p2, p0)) — a 4-point closed linestring, one triangle per pair of nested parentheses. Points are de-duplicated by exact floating-point value in first-occurrence order (two points differing even in the last bit remain distinct — no epsilon tolerance); the repeated closing point of each ring is dropped once the 3 unique corner indices are recovered. A ring whose last point doesn't equal its first raises an error ("not a closed linestring").

The C++ reader parses this by tracking parenthesis depth rather than matching literal substrings — the triangle's point list sits at depth 3 (TIN → 1, the triangle polygon → 2, its linestring → 3) — which makes it naturally tolerant of arbitrary whitespace/newlines between and inside the nested parentheses.

Cell types

triangle only — WKT never produces any other cell type.

Data mapping

None — plain Mesh(points, [CellBlock("triangle", ...)]), no point_data, cell_data, or field_data.

Quirks & limitations

• Point de-duplication is by exact value (no tolerance), so numerically- identical-but-differently-rounded coordinates are treated as distinct points if they don't parse to the exact same float.
• The write→read round trip for arbitrary meshes is currently disabled in the test suite (marked skip, pending re-enablement) — treat WKT primarily as a well-tested reader for now; the writer is implemented and does work, just not exercised by an automatic round-trip test.
• Whitespace handling is deliberately permissive on read — the reference whitespaced.wkt fixture has newlines and irregular spacing sprinkled throughout, including a point given with mixed-precision text (0.00, .1, 0.) that still parses to the same set of unique points.

Notes

• tests/meshes/wkt/simple.wkt — 2 triangles sharing an edge, 4 unique points, point-sum reference 4.
• tests/meshes/wkt/whitespaced.wkt — the same 2 triangles with irregular internal whitespace and mixed-precision coordinate text, point-sum reference 3.2.
• Fully handled by the C++ core.