Convert OFF to OBJ

off2obj.py

#!/usr/bin/env python3

import sys

num_vert, num_face, num_edge = 0, 0, 0
not_handled_lines = 0
expect_header = True
expect_count = None
expect_vertices = 0
expect_faces = 0

for line in sys.stdin:
    line = line.rstrip()
    if expect_header and line.startswith('OFF'):
        expect_count = True
        expect_header = False
    elif expect_count:
        expect_count = False
        num_vert, num_face, num_edge = tuple(map(int, line.split(' ', 2)))
        assert(num_edge == 0)
        expect_vertices = num_vert
    elif expect_vertices > 0:
        expect_vertices -= 1
        if expect_vertices == 0:
            expect_faces = num_face
        v = line.split(' ')
        assert(len(v) == 3 or len(v) == 4)
        print('v {}'.format(' '.join(v)))
    elif expect_faces > 0:
        expect_faces -= 1
        f = line.split(' ')
        assert((f[0] == '3' and len(f) == 4) or (f[0] == '4' and len(f) == 5))
        n = f[0]
        f = list(map(lambda x: int(x) + 1, f[1:])) # OBJ indexes from 1
        print('f {}'.format(' '.join(map(str, f))))
    else:
        not_handled_lines += 1

sys.stderr.write('Converted {} vertices and {} faces to OBJ\n'.format(num_vert, num_face))

if not_handled_lines > 0:
    sys.stderr.write('{} lines were not expected\n'.format(not_handled_lines))
    sys.exit(1)