调试Python乒乓球游戏

Question

我很累，今天一直在尝试运行这个程序。这是一个乒乓球游戏，球会在墙上反弹，并且会碰到用户的“板子”或叫挡板。我尝试调试了很久，结果发现我的 iCollide 和 iGet_Velocity 这两个部分出了很多问题。

from livewires import games, color
games.init (screen_width = 640, screen_height = 480, fps = 50)

class Ball (games.Sprite):
    def update (self):
        if self.right>544:
            self.dx = -self.dx
        if self.top > 11 or self.bottom > 470:
            self.dy = -self.dy
        if self.left < 0:
            self.iLost()

    def iLost (self):
        games.Message (screen = self.screen,
                       x = 340,
                       y = 240,
                       text = "Game Over",
                       size = 90,
                       color = color.red,
                       lifetime = 250,
                       after_death = self.screen.quit)                       

    def ihandle_collision (self):
        new_dx, new_dy = Slab.iVelocity()
        self.dx += self.dx + new_dx  #For handling collision, must take velocity of the mouse object and put add it to the velocity of the ball.
        self.dy += self.dy + new_dy

class Slab (games.Sprite):
    def update (self):
        self.x = games.mouse.x
        self.y = games.mouse.y
        self.iCollide()

    def iCollide (self):
        for Ball in self.overlapping_sprites:
            Ball.ihandle_collision()

    def iVelocity (self):
        self.get_velocity()


def main():
    #Backgrounds
    pingpongbackground = games.load_image ("pingpongbackground.jpg", transparent = False)
    games.screen.background = pingpongbackground
    #Ball: Initializing object and setting speed.
    ballimage = games.load_image ("pingpongball.jpg", transparent = True)
    theball = Ball (image = ballimage,
                    x = 320,
                    y = 240,
                    dx = 2,
                    dy = 2)
    games.screen.add(theball)
    #Paddle: Initializing ping pong object and setting initial poisition to the initial mouse position
    slabimage = games.load_image ("pingpongpaddle.jpg", transparent = True)
    theslab = Slab (image = slabimage,
                    x = games.mouse.x,
                    y = games.mouse.y)
    games.screen.add(theslab)
    games.mouse.is_visible = False
    games.screen.event_grab = True
    games.screen.mainloop()

main ()

Answer 1

这两行代码看起来有点可疑：

    self.dx += self.dx + new_dx
    self.dy += self.dy + new_dy

试试这个：

    self.dx += new_dx
    self.dy += new_dy

Answer 2

嗯，没有更多的数据，我不能确定问题出在哪里。不过，看起来你的碰撞反应代码有点问题。例如，在第一部分，你应该这样做，以正确处理边界条件：

def update (self):
    if self.right>544 and self.dx > 0:
        self.dx = -self.dx
    if (self.top > 11 and self.dy < 0) or (self.bottom > 470 and self.dy > 0):
        self.dy = -self.dy
    if self.left < 0:
        self.iLost()

另外，你的碰撞反应代码也有点奇怪。这段代码没有经过测试，但大致上是对的：（编辑：我加了更多注释，让它更清楚）

def iCollide (self):
    for Ball in self.overlapping_sprites:

        #Extract the components of the slab's velocity
        slab_vx, slab_vy = self.iVelocity()

        #Compute relative components of slab velocity
        rel_vx, rel_vy = Ball.dx - slab_vx, Ball.dy - slab_vy

        #Determine the time of intersection and the normal direction
        #This is done to compute which face the ball hits
        #Initially suppose that the objects intersect at t=infinity
        t, nx, ny = 100000, 0, 0

        #Check left/right faces
        if rel_vx != 0:
            #Check if ball hits left face
            toi = (self.left - Ball.right) / rel_vx
            if toi < t:
                t, nx, ny = toi, -1, 0

            #Check if ball hits right face
            toi = (self.right - Ball.left) / rel_vx

            if toi < t:
                t, nx, ny = toi, 1, 0

        #Check top/bottom faces:
        if rel_vy != 0:

            #Check if ball hits top face
            toi = (self.top - Ball.bottom) / rel_vx
            if toi < t:
                t, nx, ny = toi, 0, -1

            #Check if ball hits right face
            toi = (self.bottom - Ball.top) / rel_vx
            if toi < t:
                t, nx, ny = toi, 0, 1

        #Check if impact force properly corrects velocity
        if Ball.dx * nx + Ball.dy * ny < 0:

            #Reflect the ball's position
            Ball.dx += Ball.dx * nx * 2.0
            Ball.dy += Ball.dy * ny * 2.0

        #Check if cursor movement is not pushing ball into paddle:
        if slab_vx * nx + slab_vy * ny < 0:
            Ball.dx += slab_vx
            Ball.dy += slab.vy

你应该尝试找出球体与哪个平面相交，然后根据那个方向反射球的速度。现在这段代码并没有经过测试，因为我无法让你的例子运行。不过，它应该能给你一个正确解决方案应该做什么的概念。