在乒乓球比赛中，球和球拍碰撞时会停止，一旦球拍移动，球就会弹开

Question

我第一次用python编写pong，我试图让球在碰到球拍时反弹。现在，当球碰到球拍时会停止，然后只有当球拍移动时才会反弹。我希望球一碰到球拍就弹起来。你知道怎么解决这个问题吗？感谢您的帮助。谢谢

import pygame, random, sys
from pygame.locals import *
#set constants
WINDOWWIDTH = 600
WINDOWHEIGHT = 600
TEXTCOLOR = (255, 255, 255)
BACKGROUNDCOLOR = (0, 0, 255)
FPS = 40
BLACK = (0,0,0)
RED = (255, 0, 0)
WHITE = (255, 255, 255)
#set variables
rectY1 = 240
rectY2 = 240
Y1change = 0
Y2change = 0
ballX = 320
ballY = 240
ballXvel = 0
ballYvel = 0
paddle1 = pygame.Rect(18,rectY1,10,120)
paddle2 = pygame.Rect(620,rectY2,10,120)
ball = pygame.Rect(ballX,ballY,30,30)
#create shapes
def drawshapes():   
pygame.draw.rect(DISPLAY, WHITE, paddle1)
pygame.draw.rect(DISPLAY, WHITE, paddle2)
pygame.draw.rect(DISPLAY, WHITE, ball)
#set up display    
pygame.init
DISPLAY = pygame.display.set_mode((640,480),0,32)
pygame.display.set_caption('Pong')
fpsClock = pygame.time.Clock()
#main loop
while True:
for event in pygame.event.get():
if event.type==QUIT:
pygame.quit()
sys.exit()
if event.type == KEYDOWN :
if event.key == K_SPACE :
ballXvel += 10
ballYvel += 10
if ball.colliderect(paddle1) :
ballX = paddle1.x
ballXvel = ballXvel * -1
if ball.colliderect(paddle2) :
ballXvel = ballXvel * -1


if ballX > 620 :
ballXvel = ballXvel * -1
##    if ballX < 20 :
##        ballXvel = ballXvel * -1 
if ballY > 460 :
ballYvel = ballYvel * -1
if ballY < 20 :
ballYvel = ballYvel * -1
keys = pygame.key.get_pressed()
Y1change = 0
Y2change = 0
#make paddles move
if keys[K_UP]:
Y2change -= 10
if keys[K_DOWN]:
Y2change += 10
if keys[ord('w')]:
Y1change -= 10
if keys[ord('s')]:
Y1change += 10
#stop paddles at edges 
if rectY1 < 5 :
rectY1 = 5
if rectY1 > 355 :
rectY1 = 355
if rectY2 < 5 :
rectY2 = 5
if rectY2 > 355 :
rectY2 = 355
ball.y = ballY
ball.x = ballX
ballX += ballXvel
ballY += ballYvel
paddle1.y = rectY1
paddle2.y = rectY2
rectY1 += Y1change
rectY2 += Y2change
DISPLAY.fill(BLACK)
drawshapes()
pygame.display.update()
fpsClock.tick(FPS)

Answer 1

因为你有球拍和球的坐标，所以你所要做的就是检查球的某个部分是否"在"球拍的某个部位。

假设桨是从(0,0(到(1,1(的正方形。如果我们有一个半径为1个单位的球，如果球的中心在球拍任何边缘的1个单位内，我们就知道它与球拍相交。

编辑：这个答案更加详细。

Answer 2

在进行碰撞测试之前而不是之后移动球。由于球的步数大于1，所以球不会准确地击中球拍。如果球打在左球拍上，那么你必须把球的左侧放在球拍的右侧。如果球打在右边的球拍上，你必须把球的右边放在球拍的左边
以类似的方式，您必须将球的位置限制在窗口中：
(注意ballX，ballY是球的左上角(

while True:
# [...]
ballX += ballXvel
ballY += ballYvel
if ball.colliderect(paddle1) :
ballXvel *= -1
ballX = paddle1.right
if ball.colliderect(paddle2) :
ballXvel *= -1
ballX = paddle2.left - ball.width
size = DISPLAY.get_size()
if not 0 <= ballX < size[0] - ball.width:
ballXvel *= -1
ballX = max(0, min(size[0] - ball.width, ballX))
if not 0 <= ballY < size[1] - ball.height:
ballYvel *= -1
ballY = max(0, min(size[1] - ball.height, ballY))
# [...]
ball.y = ballY
ball.x = ballX
# ballX += ballXvel <-- DELETE
# ballY += ballYvel