How do I set collision detection for Pong in Pygame

Question

I am building a Pong clone in Pygame. I can't figure out how to add collision detection to the ball and paddles so the ball will bounce off the paddles. How can I do this? How can I have the ball go the opposite direction when it hits the paddles?

bif="bg.jpg"

import pygame, sys
from pygame.locals import *

pygame.init()
pygame.display.set_caption("Griffin West's Python Pong")
pygame.mixer.init()
sounda= pygame.mixer.Sound("Music.wav")

sounda.play()

screen=pygame.display.set_mode((1280,720),0,32)
background=pygame.image.load(bif).convert()

color1=(255,255,255)
color2=(255,255,0)
color3=(0,0,255)
color4=(0,255,0)
pos1=(640,0)
pos2=(640,720)
pos3=(640,360)
pos4=(0,360)
pos5=(1280,360)
radius=(100)
x1,y1=75,0
x2,y2=1175,0
x3,y3=1,1
clock=pygame.time.Clock()
speedx=750
speedy=750
movex1, movey1=0,0
movex2, movey2=0,0
s1=0
s2=0


while True:


    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type==KEYDOWN:
            if event.key==K_w:
                movey1=-2
            elif event.key==K_s:
                movey1=+2
            if event.key==K_UP:
                movey2=-2
            elif event.key==K_DOWN:
                movey2=+2
        if event.type==KEYUP:
            if event.key==K_w:
                movey1=0
            elif event.key==K_s:
                movey1=0
            if event.key==K_UP:
                movey2=0
            elif event.key==K_DOWN:
                movey2=0

    x1+=movex1
    y1+=movey1
    x2+=movex2
    y2+=movey2


    milli=clock.tick()
    seconds=milli/1000.0
    dx=seconds*speedx
    dy=seconds*speedy
    x3+=dx
    y3+=dy

    if x3>1280: 
        x3+=-dx  # get ball out of the wall
        speedx = -speedx  # change direction
        s1=s1+1
    if y3>720:
        y3+=-dy
        speedy = -speedy
    if x3<0:
        x3+dx
        speedx = -speedx
        x3=x3+1
        s2=s2+1
    if y3<0:
        y3=y3+1
        y3+=dy
        speedy = -speedy
    if x3<=y3y3+30:
        speedx = -speedy


    screen.blit(background, (0,0))

    screen.lock()
    pygame.draw.line(screen, color1, pos1, pos2, 1)
    pygame.draw.circle(screen, color1, pos3, radius, 1)
    pygame.draw.circle(screen, color1, pos4, radius, 1)
    pygame.draw.circle(screen, color1, pos5, radius, 1)
    pygame.draw.rect(screen, color3, Rect((x1,y1),(30,100)))
    pygame.draw.rect(screen, color2, Rect((x2,y2),(30,100)))
    pygame.draw.circle(screen, color4, (int(x3),int(y3)), 15)

    screen.unlock()
    myfont = pygame.font.SysFont("Press Start 2P", 50)
    myfont2 = pygame.font.SysFont("Press Start 2P", 25)
    label = myfont.render("Python", 1, (255,0,0))
    screen.blit(label, (494, 115))
    label = myfont.render("Pong", 1, (255,0,0))
    screen.blit(label, (544, 175))
    label = myfont2.render("Player 1: "+str(s1), 1, (255,255,255))
    screen.blit(label, (25, 675))
    label = myfont2.render("Player 2: "+str(s2), 1, (255,255,255))
    screen.blit(label, (950, 675))
    pygame.display.update()

Community · Accepted Answer · 2017-05-23 12:21:21Z

This answer has a sample pong implementation that includes collision detection. Specifically, you would be interested in the bounce methods in the code as listed below.

In the Pong class:

def move_all(self):
    for obj in self.p1, self.p2, self.ball:
        obj.move()
        if obj is not self.ball:
            obj.bounce(self.ball)

In the Paddle class:

def bounce(self, ball):
    minimum = self.size.x + ball.radius
    if self.position.x != ball.position.x and self.overlap(ball, minimum):
        if not self.just_bounced:
            self.just_bounced = True
            self.score += abs(ball.velocity.y)
        sign = +1 if self.position.x < ball.position.x else -1
        if self.collision_area == self.PART.center:
            ball.position.x = self.position.x + minimum * sign
        else:
            ball.position.adjust(self.middle_point, minimum)
        ball.velocity.x = copy_sign(ball.velocity.x, sign)
        ball.change_speed()
    else:
        self.just_bounced = False

In the Ball class:

def bounce(self):
    if self.position.y - self.radius < 0:
        self.position.y = self.radius
        self.velocity.y = copy_sign(self.velocity.y, +1)
        self.change_speed()
    elif self.position.y + self.radius > self.board.y:
        self.position.y = self.board.y - self.radius
        self.velocity.y = copy_sign(self.velocity.y, -1)
        self.change_speed()

schlow · Accepted Answer · 2013-01-25 04:25:36Z

0

Make an if statement that checks if the x-coordinate of the ball went beyond the x-coordinate of the paddle and whether it's y-coordinate is within the top and bottom y-coordinate of the paddle. If so, multiply the x velocity of the ball by -1.

answered Jan 25, 2013 at 4:25

schlow

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