def resolve_ball_wall_collision(ball: PoolBall, wall: Direction):
"""
Sets the new velocity for this ball after it has collided with a wall.
*Assumes wall is in one of 4 directions: N, E, S, or W*
:param ball: pool ball
:param wall: which wall (N, E, S, W)
"""
if wall == Direction.NORTH or wall == Direction.SOUTH:
ball.vel = Vector(ball.vel.x, -ball.vel.y) # Reverse y-direction
else: # EAST or WEST
ball.vel = Vector(-ball.vel.x, ball.vel.y) # Reverse x-direction
def resolve_ball_ball_collision(a: PoolBall, b: PoolBall):
"""
Sets new velocity vectors after a ball-ball collision.
:param a: ball A
:param b: ball B
"""
# Taken from https://en.wikipedia.org/wiki/Elastic_collision#Two-dimensional_collision_with_two_moving_objects
a_vel_new = a.vel - (2 * b.mass) / (a.mass + b.mass) * (
(a.vel - b.vel).dot_product(a.pos - b.pos)
) / get_distance(a.pos - b.pos)**2 * (a.pos - b.pos)
b_vel_new = b.vel - (2 * a.mass) / (a.mass + b.mass) * (
(b.vel - a.vel).dot_product(b.pos - a.pos)
) / get_distance(b.pos - a.pos)**2 * (b.pos - a.pos)
a.vel, b.vel = a_vel_new, b_vel_new