XYZ (.xyz, .xyzn, .xyzrgb, .asc, .pts, .txt)

Headerless ASCII point clouds: one point per line, columns separated by whitespace, commas or semicolons; blank lines and # / // comments are skipped. XYZ is a convention, not a specification, so the column meaning is resolved in this order: an explicit columns= list; a header comment naming the columns (# x y z nx ny nz, what the writer emits); the column count and the file extension (3 = xyz, 4 = xyz + scalar, 6 = by extension or by value range, .pts with 7 = xyz + intensity + rgb); anything still ambiguous is an error asking for the list.

Format name	xyz
Extensions	.xyz, .xyzn, .xyzrgb, .asc, .pts, .txt (except Z88's fixed file names z88i1.txt, z88structure.txt, z88o2.txt, z88o3.txt, which are Z88)
Read / Write	✓ / ✓
Extra dependencies	—

Reading & writing

import meshioplusplus

mesh = meshioplusplus.read("cloud.xyz")
meshioplusplus.xyz.write("out.xyz", mesh)
mesh = meshioplusplus.xyz.read("odd.xyz", columns=["x", "y", "z", "_", "p"])

• columns — one name per column: x y z nx ny nz r g b a, any other name is a scalar, _ skips the column. Empty = infer.
• delimiter — column delimiter. Empty = detect (;, then ,, else whitespace).
• float_fmt (write) — a format spec such as ".16e"; by default float32 columns use .9g and the rest .17g.

Mesh mapping

Float64 points plus one vertex block — what subsample_points produces. Columns nx ny nz → "normals" (n, 3); r g b [a] → "rgb" / "rgba" uint8 (byte values, or unit floats scaled by 255); every other named column is a float64 scalar under its own name.

Quirks & limitations

• Chemistry XYZ shares the extension (atom count on line 1, comment on line 2, element symbols in column 1). It is detected and refused with a message naming it — meshio++ has no reader for it.
• Six columns are ambiguous by count alone (xyz + normals or RGB): resolved by value range (unit vectors are normals, byte-valued integers are colours), overridable by extension (.xyzn / .xyzrgb) or by columns=.
• .pts files start with a point count that is validated against the rows found.
• Only vertex cells are writable (anything else is skipped with a warning); all cell data is dropped. Points below 3D are padded with zeros.

Notes

• The C++ core and the Python reference are byte-identical (same header comment, same float formatting).

Web output

An XYZ cloud is a vertex block (or no cells at all), which the glTF writer turns into a POINTS primitive, keeping the normals point data as NORMAL and every other point array as a raw _NAME attribute: meshioplusplus convert cloud.xyz cloud.glb puts a scanned cloud on the web. Run compute_normals first when the cloud has none.