配套视频教程
本节最终效果：
image
一个游戏大致可以分为以下几个标准处理过程：
init() 初始化
new() 游戏初次进入（或主角挂了，重新开始时）
update() 游戏逻辑更新
events() 事件处理（响应键盘、鼠标等事件）
draw() 屏幕渲染绘制
show_start_screen() 游戏的启动画面
show_go_screen() 游戏结束时的画面
run() 游戏运行的循环入口
我们将上节的游戏模板，实现成一个Game类：
import pygame as pg
import random
from settings import *
from sprites import *
class Game:
def __init__(self):
# initialize game window, etc
pg.init()
pg.mixer.init()
self.screen = pg.display.set_mode((WIDTH, HEIGHT))
pg.display.set_caption(TITLE)
self.clock = pg.time.Clock()
self.running = True
def new(self):
# start a new game
self.all_sprites = pg.sprite.Group()
self.player = Player()
self.all_sprites.add(self.player)
self.run()
def run(self):
# Game Loop
self.playing = True
while self.playing:
self.clock.tick(FPS)
self.events()
self.update()
self.draw()
# 为了方便观察pos,vel,acc这些变量，定义一个debug辅助函数
def debug(self):
font = pg.font.SysFont('Menlo', 25, True)
pos_txt = font.render(
'Pos:(' + str(round(self.player.pos.x, 2)) + "," + str(round(self.player.pos.y, 2)) + ")", 1, GREEN)
vel_txt = font.render(
'Vel:(' + str(round(self.player.vel.x, 2)) + "," + str(round(self.player.vel.y, 2)) + ")", 1, GREEN)
acc_txt = font.render(
'Acc:(' + str(round(self.player.acc.x, 2)) + "," + str(round(self.player.acc.y, 2)) + ")", 1, GREEN)
self.screen.blit(pos_txt, (20, 10))
self.screen.blit(vel_txt, (20, 40))
self.screen.blit(acc_txt, (20, 70))
def update(self):
# Game Loop - Update
self.all_sprites.update()
def events(self):
# Game Loop - events
for event in pg.event.get():
# check for closing window
if event.type == pg.QUIT:
if self.playing:
self.playing = False
self.running = False
def draw(self):
# Game Loop - draw
self.screen.fill(BLACK)
self.all_sprites.draw(self.screen)
# *after* drawing everything, flip the display
self.debug()
pg.display.flip()
def show_start_screen(self):
# game splash/start screen
pass
def show_go_screen(self):
# game over/continue
pass
g = Game()
g.show_start_screen()
while g.running:
g.new()
g.show_go_screen()
pg.quit()
注：有2个控制变量，running是控制pygame是否退出，而playing是游戏情节是否继续处理
(即：有可能游戏情况结束，比如：主角挂了，显示game over，但是pygame并不需要退出，可以选择重新开始）
settings.py
TITLE = "Rabbit jump on the sky!"
WIDTH = 480
HEIGHT = 600
FPS = 60
# Player properties
PLAYER_ACC = 0.5
PLAYER_FRICTION = -0.12
# define colors
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
YELLOW = (255, 255, 0)
定义游戏的精灵(下面代码命名为sprites.py)
# Sprite classes for platform game
import pygame as pg
from settings import *
vec = pg.math.Vector2
class Player(pg.sprite.Sprite):
def __init__(self):
pg.sprite.Sprite.__init__(self)
self.image = pg.Surface((30, 40))
self.image.fill(YELLOW)
self.rect = self.image.get_rect()
self.rect.center = (WIDTH / 2, HEIGHT / 2)
self.pos = vec(WIDTH / 2, HEIGHT / 2)
self.vel = vec(0, 0)
self.acc = vec(0, 0)
def update(self):
self.acc = vec(0, 0)
keys = pg.key.get_pressed()
if keys[pg.K_LEFT]:
self.acc.x = -PLAYER_ACC
if keys[pg.K_RIGHT]:
self.acc.x = PLAYER_ACC
# apply friction
self.acc += self.vel * PLAYER_FRICTION
# equations of motion
self.vel += self.acc
self.pos += self.vel + 0.5 * self.acc
# wrap around the sides of the screen
if self.pos.x > WIDTH:
self.pos.x = 0
if self.pos.x < 0:
self.pos.x = WIDTH
self.rect.center = self.pos
-
在2D游戏中，会大量用到类似(x,y)的结构，pygame中已经把这种结构封装成了Vector2.
-
加速度的定义：单位时间内速度的变化量。在游戏中，单位时间就是每帧，所以每一帧，我们在速度self.vel（velocity的缩写）值上的改变即为加速度self.acc( acceleration的缩写），因为
v=a*t
这里t可以理解为1.
3.计算player新位移
self.pos += self.vel + 0.5 * self.acc
使用位移公式（t同样理解为1），1帧
s = v*t+1/2*a*t**2
- 摩擦力的效果
PLAYER_FRICTION = -0.12
self.acc += self.vel * PLAYER_FRICTION
self.vel += self.acc
等价于
self.acc = self.acc + self.vel * PLAYER_FRICTION
self.vel = self.vel + self.acc
也即：
PLAYER_FRICTION = -0.12
self.vel = self.vel + self.vel * PLAYER_FRICTION
摩擦力的效果，表现为阻碍物体运动，具体在代码中体现，只要想办法把速度减少一点点。以上代码实现了该效果。
image
可以通过调试观察到，方块向右，速度由0变正，再由于摩擦力的作用变为0；反之相反。方块向右，加速度由正及负最后变为0，反之相反。速度为正，方块位置增加（表现为向右移动）；速度为负，方块位置减小（表现为向左移动）；方块向右，加速度为正，使得速度变大（正的大），方块向左，加速度为负，使得速度变大（负的大，实际上是变小）
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