查找两个向量和它们之间的角度

Question

[我有一辆汽车和一个代表行人的点，我能够找到向量a和b（请参见下图），然后尝试计算它们之间的角度]

我使用已知公式cos（角度）=幅度（vector_a）*幅度（vector_a））/ dot_product（vector_a，vector_b），但是当我计算余弦时，它比一个大得多，因此无法计算角度。 ..我在做什么错？

    def detect_pedestrian(car,pedestrian):
        #Find a vector which connects pedestrian with a car
        pedestrian_position = pedestrian.body.position
        car_position = car.body.position

        #Find vectors a and b
        car_vector = Box2D.b2Body.__GetTransform(car.body).R.GetYAxis()
        pedestrian_vector = pedestrian_position - car_position

        #Calculate magnitudes of both vector
        pedestrian_vector_magnitude = np.linalg.norm(pedestrian_vector)
        car_vector_magnitude = np.linalg.norm(car_vector)

        #Normalize both vectors
        pedestrian_vector_normalized = pedestrian_vector/pedestrian_vector_magnitude
        car_vector_normalized = car_vector/car_vector_magnitude

        #Calculate angle
        magnitudes = pedestrian_vector_magnitude * car_vector_magnitude
        dot_product = b2Dot(pedestrian_vector_normalized, car_vector_normalized)
        cosine = magnitudes/dot_product
        arccos = np.arccos(cosine)

        print(cosine)

非常感谢

Answer 1

您需要汽车的heading