The Thing (2002) msh to obj converter

thing_convert.py

import struct
import sys

verts_start = 0xA4
vert_count = 0x2B
vert_format = "<I 3f 3f 2f"
vert_size = struct.calcsize(vert_format)

indices_start = 0x6B8
indices_count = 0x84
face_format = "<3H"
face_size = struct.calcsize(face_format)

# obj outputs
vert_coord = []
vert_tex = []
vert_norm = []
faces = []

with open("flamerfuel-flame-thrower.msh", "rb") as msh:
    for o_v in range(verts_start, verts_start + vert_count * vert_size, vert_size):
        msh.seek(o_v)
        v = struct.unpack(vert_format, msh.read(vert_size))
        # print(f"{hex(o_v)}: {v}")
        vert_coord.append((v[1], v[2], v[3]))
        vert_norm.append((v[4], v[5], v[6]))
        vert_tex.append((v[7], v[8]))

    for o_f in range(indices_start, indices_start + indices_count * 2, face_size):
        msh.seek(o_f)
        f = struct.unpack(face_format, msh.read(face_size))
        faces.append(f)

for x, y, z in vert_coord:
    print(f"v {x} {y} {z}")

for u, v in vert_tex:
    print(f"vt {u} {v}")

for i, j, k in vert_norm:
    print(f"vn {i} {j} {k}")

for v0, v1, v2 in faces:
    print(f"f {v0 + 1}/{v0 + 1}/{v0 + 1} {v1 + 1}/{v1 + 1}/{v1 + 1} {v2 + 1}/{v2 + 1}/{v2 + 1}")