def export_obj(vertices, triangles, filename):
    """
    Exports a mesh in the (.obj) format.
    """
    with open(filename, 'w') as fh:
        for v in vertices:
            fh.write('v {} {} {}\n'.format(*v))
        for f in triangles:
            fh.write('f {} {} {}\n'.format(*(f + 1)))
