tracing image in pygame

Question

lately I've been trying to create a ping pong game with Pygame but I can't seem to figure out why? or how the ball started tracing when I made it a moving object in the game. how can I go about fixing this problem?

import pygame, sys

def ball_ani():
    global speedx, speedy
    ball.x += speedx
    ball.y += speedy

    if ball.top <= 0 or ball.bottom >= h:
        speedy *= -1
    if ball.left <= 0 or ball.right >= w:
        speedx *= -1
    
    if ball.colliderect(player) or ball.colliderect(player2):
        speedx *= -1

pygame.init()
clock = pygame.time.Clock()

w, h = 1000, 500

pygame.display.set_caption('Fut Pong')
win = pygame.display.set_mode((w, h))
win.fill("black")
pygame.draw.line(win, "white", (w//2, 0), (w//2, h), 3)

ball = pygame.Rect(w//2 - 10, h//2 - 10, 20, 20)
player = pygame.Rect(w - 15, h//2 - 50, 10, 100)
player2 = pygame.Rect(5, h//2 - 50, 10, 100)

speedx, speedy = 7, 7

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            sys.exit()

    ball_ani()

    pygame.draw.ellipse(win, "green", ball)
    pygame.draw.rect(win, "white", player)
    pygame.draw.rect(win, "white", player2)

    pygame.display.flip()
    clock.tick(60)

Rabbid76 · Accepted Answer · 2022-02-18T20:40:49.920

2

You must clear the display in ever frame:

run = True
while run:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = Fasle

    ball_ani()

    win.fill("black") # <--- this is missing

    pygame.draw.ellipse(win, "green", ball)
    pygame.draw.rect(win, "white", player)
    pygame.draw.rect(win, "white", player2)

    pygame.display.flip()
    clock.tick(60)

pygame.quit()
exit()

The typical PyGame application loop has to:

limit the frames per second to limit CPU usage with pygame.time.Clock.tick
handle the events by calling either pygame.event.pump() or pygame.event.get().
update the game states and positions of objects dependent on the input events and time (respectively frames)
clear the entire display or draw the background
draw the entire scene (blit all the objects)
update the display by calling either pygame.display.update() or pygame.display.flip()

edited Feb 18 '22 at 20:40

answered Sep 19 '21 at 09:58

Rabbid76

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@hc_dev `cleat` is a typo. Compare [`pygame.quit()`](https://www.pygame.org/docs/ref/pygame.html#pygame.quit) and [`sys.exit()`](https://docs.python.org/3/library/sys.html#sys.exit) – Rabbid76 Feb 18 '22 at 20:43
1

Thanks, for the direction .. will study deeper, just saw my intuition confirmed in [official docs example](https://www.pygame.org/docs/tut/PygameIntro.html?highlight=quit#taste): `if event.type == pygame.QUIT: sys.exit()` (explained as "simply exit the program, pygame will ensure everything is cleanly shutdown."). Learned something new. – hc_dev Feb 18 '22 at 20:52

tracing image in pygame

1 Answers1