def turn(self, rotate):
angle = Geometry.standard(rotate - self.toward)
if not angle:
return
direct = self.velocity if angle > 0 else -self.velocity #顺时针或逆时针的步长
self.residual += abs(angle) #需要旋转的总长度
start = self.toward
while self.residual >= self.velocity: #还能再旋转一个时间片
end = start + direct
if (end - rotate) * direct > 0:
end = rotate
yield {'type': 'rotate', 'start': start, 'end': end}
self.residual -= self.velocity
start = end
self.toward = rotate
