Leapfrog Geo's msh file reader and converter to Wavefront .obj

msh.py

# Contributors: Alexander Jüstel, Arthur Endlein Correia, Florian Wellmann
#
# This script is part of GemGIS, saved here as a standalone version.
#
# GemGIS is a Python-based, open-source geographic information processing library.
# It is capable of preprocessing spatial data such as vector data (shape files, geojson files, geopackages),
# raster data, data obtained from WMS services or XML/KML files.
#
# Preprocessed data can be stored in a dedicated Data Class to be passed to the geomodeling package GemPy
# in order to accelerate to model building process.
#
# GemGIS is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# GemGIS is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License (LICENSE.md) for more details.

import numpy as np
from pathlib import Path

dtype_conversion = {
    "Integer": np.int32,
    "Double": np.float64
}

def read_msh(fname):
    with open(fname, "rb") as f:
        header = []
        chunk = f.read(512)
        header_end = chunk.find(b"[binary]")
        data = {}
        f.seek(header_end + 0x14)
        for line in chunk[chunk.find(b"[index]") + 8:header_end].decode("utf-8").strip().split("\n"):
            name, dtype, *shape = line.strip().rstrip(";").split()
            shape = list(map(int, reversed(shape)))
            dtype = dtype_conversion[dtype]
            data[name] = np.fromfile(
                f,
                dtype,
                np.prod(shape)
            ).reshape(shape)
    return data

def save_obj(data, fname):
    with open(fname, "w") as f:
        f.write("".join([f"v {x} {y} {z}\n" for x, y, z in data["Location"]]))
        f.write("".join([f"f {i} {j} {k}\n" for i, j, k in data["Tri"] + 1]))


if __name__ == "__main__":
    from sys import argv
    if len(argv) < 2:
        print("usage: python msh.py INPUT [OUTPUT]\n If output is not given, the input name will be used with extension changed to .obj")
        exit()
    _, msh, *obj = argv
    msh = Path(msh)
    if not obj:
        obj = msh.with_suffix(".obj")
    else:
        obj = Path(obj[0])
    data = read_msh(msh)
    save_obj(data, obj)