stl_utils.py 文件源码

def _binary_write(filepath, faces):
    with open(filepath, 'wb') as data:
        fw = data.write
        # header
        # we write padding at header beginning to avoid to
        # call len(list(faces)) which may be expensive
        fw(struct.calcsize('<80sI') * b'\0')

        # 3 vertex == 9f
        pack = struct.Struct('<9f').pack

        # number of vertices written
        nb = 0

        for face in faces:
            # calculate face normal
            # write normal + vertexes + pad as attributes
            fw(struct.pack('<3f', *normal(*face)) + pack(*itertools.chain.from_iterable(face)))
            # attribute byte count (unused)
            fw(b'\0\0')
            nb += 1

        # header, with correct value now
        data.seek(0)
        fw(struct.pack('<80sI', _header_version().encode('ascii'), nb))