Question

I have been trying to animate drawing elements without success. I can animate imported images, but when I try to animate drawings generated by pygame they remain static.

Edit: By “animate” I mean “to move”. As in making a circle move in x and y direction.

This is my code:

import pygame, sys
from pygame.locals import *

pygame.init()

FPS = 60
WIDTH = 600
HEIGHT = 500
fpsClock = pygame.time.Clock()
DISPLAYSURF = pygame.display.set_mode((WIDTH, HEIGHT), 0, 32)
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
ballx = WIDTH / 2
bally = HEIGHT / 2
ball_vel = [1, 1]
ball_pos =(ballx, bally)
RADIUS = 20

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

    # Erase the screen (I have tried with and without this step)
    DISPLAYSURF.fill(BLACK)

    # Update circle position
    ballx += ball_vel[0]
    bally += ball_vel[1]

    # Draw Circle (I have tried with and without locks/unlocks)
    DISPLAYSURF.lock()
    pygame.draw.circle(DISPLAYSURF, WHITE, ball_pos, RADIUS, 2)
    DISPLAYSURF.unlock()

    # Update the screen
    pygame.display.update()
    fpsClock.tick(FPS)

I’ve tried with and without locking/unlocking the display surface (as the documentation suggests). I’ve tried with and without erasing the screen before updating it (as some tutorials suggest). I just can’t get it to work.

What am I doing wrong? How do you animate drawing elements?

Thanks for your time.

Answer 1

You are not updating the ball_pos tuple: you set it to the start coordinates:

ballx = WIDTH / 2
bally = HEIGHT / 2
ball_vel = [1, 1]
ball_pos =(ballx, bally)

You later update ballx and bally, but never set ball_pos again to ballx, and bally.
In the while loop, after setting the ballx and bally, do this:

ball_pos = (ballx,bally)