Writes PLY files.

Rows are accumulated as iodata and handed to the file in batches. Building output by appending binaries (acc <> row) copies the whole accumulator on every row, turning a linear write into a quadratic one; iodata avoids that.

Element data is written in the header's declared order, and each row is serialised in property order — that order is the on-disk layout.

Values are validated before they are encoded

Binary encoding silently truncates: 300 written as uchar becomes 44, a float too large for float32 becomes infinity, and a 256-item list with a uchar count writes a length of zero — which then reads back as an empty list through this library's own reader, losing the data without ever reporting an error. Every value is therefore range-checked first, and a violation returns {:error, %Ply.Error{}} naming the row and property.

Writing is atomic

Output goes to a temporary file in the destination directory and is renamed into place only after every row has been written and the declared counts verified. A validation failure part-way through would otherwise leave a truncated file with a header that lies about its contents — and would destroy an existing valid file at that path.