visible_vertices.py 文件源码

def angle(center, point):
    """Return the angle (radian) of point from center of the radian circle.
     ------p
     |   /
     |  /
    c|a/
    """
    dx = point.x - center.x
    dy = point.y - center.y
    if dx == 0:
        if dy < 0:
            return pi * 3 / 2
        return pi / 2
    if dy == 0:
        if dx < 0:
            return pi
        return 0
    if dx < 0:
        return pi + atan(dy / dx)
    if dy < 0:
        return 2 * pi + atan(dy / dx)
    return atan(dy / dx)