Un ciclo de caminata

Parte de la sección Mundos del Journey de Pygame de Coddy. Lección 26 de 35.

Un blob que se desliza con una sola imagen parece congelado. El paquete tiene una segunda pose, blob_walk.png, con los pies en otra posición. Mostrar las dos alternativamente hace que camine.

Mantén ambas poses en una lista y un contador de fotogramas en el sprite. En cada actualización, incrementa el contador y elige una pose a partir del valor:

self.frames = [blob_img, blob_walk_img]
self.timer = 0
# en update
self.timer += 1
self.image = self.frames[self.timer // 10 % 2]

self.timer // 10 aumenta en uno cada 10 fotogramas, y % 2 lo convierte en 0, 1, 0, 1. Cada pose se muestra durante 10 fotogramas, seis pasos por segundo. Un número menor que 10 hace que los pies se muevan más rápido.

El bucle de dibujo ya dibuja blob.image, así que basta con cambiar self.image.

Desafío

Fácil

En Blob.__init__, crea self.frames = [blob_img, blob_walk_img] y self.timer = 0 (blob_walk_img se carga en el código inicial).
Al principio de update, suma 1 a self.timer y establece self.image = self.frames[self.timer // 10 % 2].

Pruébalo tú mismo

import pygame

TILE = 36
SPEED = 4
GRAVITY = 1
JUMP = -15
MAX_FALL = 12

LEVEL = [
    "................",
    "................",
    "................",
    "................",
    "..........####..",
    "................",
    "...####.........",
    "................",
    "#.P............#",
    "################",
]

pygame.init()
screen = pygame.display.set_mode((576, 360))
pygame.display.set_caption("Walk Cycle")
clock = pygame.time.Clock()

background = pygame.image.load("assets/backgrounds/clouds.png").convert_alpha()
block_img = pygame.image.load("assets/images/block.png").convert_alpha()
player_img = pygame.image.load("assets/images/player.png").convert_alpha()
blob_img = pygame.image.load("assets/images/blob.png").convert_alpha()
blob_walk_img = pygame.image.load("assets/images/blob_walk.png").convert_alpha()


class Blob(pygame.sprite.Sprite):
    def __init__(self, midbottom):
        super().__init__()
        self.image = blob_img
        self.rect = pygame.Rect(0, 0, 30, 26)
        self.rect.midbottom = midbottom
        self.direction = 1

    def update(self):
        self.rect.x += self.direction
        if self.direction > 0:
            ahead = self.rect.right
        else:
            ahead = self.rect.left - 1
        hit_wall = any(self.rect.colliderect(wall) for wall in walls)
        ground_ahead = any(wall.collidepoint(ahead, self.rect.bottom) for wall in walls)
        if hit_wall or not ground_ahead:
            self.rect.x -= self.direction
            self.direction = -self.direction

walls = []
for row, line in enumerate(LEVEL):
    for col, char in enumerate(line):
        if char == "#":
            walls.append(pygame.Rect(col * TILE, row * TILE, TILE, TILE))
        elif char == "P":
            start = (col * TILE + TILE // 2, row * TILE + TILE)

blobs = pygame.sprite.Group(Blob((432, 144)), Blob((432, 324)))
player = player_img.get_rect(midbottom=start)
vel_y = 0
on_ground = False

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN and event.key in (pygame.K_SPACE, pygame.K_UP):
            if on_ground:
                vel_y = JUMP
        elif event.type == pygame.KEYUP and event.key in (pygame.K_SPACE, pygame.K_UP):
            if vel_y < -4:
                vel_y = -4

    keys = pygame.key.get_pressed()
    dx = 0
    if keys[pygame.K_LEFT]:
        dx -= SPEED
    if keys[pygame.K_RIGHT]:
        dx += SPEED

    player.x += dx
    for wall in walls:
        if player.colliderect(wall):
            if dx > 0:
                player.right = wall.left
            elif dx < 0:
                player.left = wall.right

    vel_y = min(vel_y + GRAVITY, MAX_FALL)
    player.y += vel_y
    on_ground = False
    for wall in walls:
        if player.colliderect(wall):
            if vel_y > 0:
                player.bottom = wall.top
                on_ground = True
            elif vel_y < 0:
                player.top = wall.bottom
            vel_y = 0

    blobs.update()

    for blob in blobs:
        if player.colliderect(blob.rect):
            if vel_y > 0 and player.bottom < blob.rect.centery:
                blob.kill()
                vel_y = -8
            else:
                player.midbottom = start
                vel_y = 0

    for y in range(0, 360, 72):
        for x in range(0, 576, 72):
            screen.blit(background, (x, y))
    for wall in walls:
        screen.blit(block_img, wall)
    for blob in blobs:
        screen.blit(blob.image, blob.image.get_rect(midbottom=blob.rect.midbottom))
    screen.blit(player_img, player)
    pygame.display.flip()
    clock.tick(60)

pygame.quit()