pygame中的加速和减速

如何解决pygame中的加速和减速

我没有太多的编码经验，我一直试图让我的角色在按住键时加速到恒定速度并在松开键时减速。我在网上找到了一些代码，但我似乎无法将它正确地应用到我的代码中。如果你不介意的话，如果你彻底解释了答案会很有帮助，这样我就可以正确地理解我做错了什么。

这是我的代码

"""Dot Game"""

#Imports
import pygame,sys

#Constants
WIDTH,HEIGHT = 1000,1000
TITLE = "Dot."

#pygame initialization
pygame.init()
win = pygame.display.set_mode((WIDTH,HEIGHT))
pygame.display.set_caption(TITLE)
#fps
FPS = 60
fpsclock = pygame.time.Clock()

#colors
bgc = (247,226,222)
pc = (152,193,217)
pc2 = (61,90,128)
ec = (119,2,26)
ec2 = (220,66,73)

#accel
x_change = 0
y_change = 0
accel_x = 0
accel_y = 0
max_speed = 6

display_width,display_height = pygame.display.get_surface().get_size()
x = display_width * 0.45
y = display_height * 0.8

#Player Class
class Player:
    def __init__(self,x,y):
        self.x = int(x)
        self.y = int(y)
        self.radius = 32
        self.width = 2
        self.color = pc
        self.color2 = pc2
        self.velX = 0
        self.velY = 0
        self.left_pressed = False
        self.right_pressed = False
        self.up_pressed = False
        self.down_pressed = False
        self.speed = 3
        self.hitBox = (self.x -20,self.y -20,40,40)
    
    def draw(self,win):
        pygame.draw.circle(win,self.color2,(self.x,self.y),20)
        pygame.draw.circle(win,self.color,14)
        self.hitBox = (self.x -20,40)
        #pygame.draw.rect(win,(255,0),self.hitBox,2)
    
    def update(self):
        self.velX = 0
        self.velY = 0
        if self.left_pressed:
            self.velX = -self.speed
        if self.right_pressed:
            self.velX = self.speed
        if self.up_pressed:
            self.velY = -self.speed
        if self.down_pressed :
            self.velY = self.speed
        
        self.x += self.velX
        self.y += self.velY

        self.rect = pygame.Rect(int(self.x),int(self.y),32,32)

    def collide(self):
        print('hit')
        pass

#Player Initialization
player = Player(WIDTH/2,HEIGHT/2)

#Main Loop
collide = False
while not collide:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            collide == True
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                accel_x = -.2
                player.left_pressed = True
            elif event.key == pygame.K_RIGHT:
                accel_x = .2
                player.right_pressed = True
            elif event.key == pygame.K_UP:
                accel_y = -.2
                player.up_pressed = True
            elif event.key == pygame.K_DOWN:
                accel_y = .2
                player.down_pressed = True
        elif event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT:
                accel_x = 0
                accel_y = 0
                player.left_pressed = False
            elif event.key == pygame.K_RIGHT:
                accel_x = 0
                accel_y = 0
                player.right_pressed = False
            elif event.key == pygame.K_UP:
                accel_x = 0
                accel_y = 0
                player.up_pressed = False
            elif event.key == pygame.K_DOWN:
                accel_x = 0
                accel_y = 0
                player.down_pressed = False
    
    x_change += accel_x  # Accelerate.
    if abs(x_change) >= max_speed:  # If max_speed is exceeded.
        # normalize the x_change and multiply it with the max_speed.
        x_change = x_change/abs(x_change) * max_speed

    y_change += accel_y  # Accelerate.
    if abs(y_change) >= max_speed:  # If max_speed is exceeded.
        # normalize the x_change and multiply it with the max_speed.
        y_change = y_change/abs(y_change) * max_speed

    # Decelerate if no key is pressed.
    if accel_x == 0:
        if x_change > 0:
            x_change -= 0.2
            if x_change < 0.2:
                x_change = 0
        elif x_change < 0:
            x_change += 0.2
            if x_change > -0.2:
                x_change = 0
    if accel_y == 0:
        if y_change > 0:
            y_change -= 0.2
            if y_change < 0.2:
                y_change = 0
        elif y_change < 0:
            y_change += 0.2
            if y_change > -0.2:
                y_change = 0

    x += x_change  # Move the object.
    y += y_change

    #Draw
    win.fill((bgc))  
    player.draw(win)

    #update
    player.update()
    pygame.display.update()

    fpsclock.tick(FPS)

运动本身有效，但没有加速和减速

解决方法

在您的代码中，速度始终保持不变，因为您在 self.velX = 0 的开头设置了 self.velY = 0 和update。因此速度的量总是0或3。 不要重置 self.velX 和 self.velY。用加速度改变速度，但限制在最大速度。加速度必须是一个小值。只要按下一个键，这个小值就会被添加到每帧一次的速度上。这会慢慢将速度提高到最大。
通过将速度乘以摩擦来提高物理性能。摩擦的值必须小于 1，否则为 1 表示没有摩擦：

class Player:
    def __init__(self,x,y):
        # [...]

        self.acceleration = 0.1
        self.friction = 0.99 # = 1   if you don't want any friction

    def update(self):
        if self.left_pressed:
            if self.velX > -max_speed:
                self.velX -= self.acceleration
        if self.right_pressed:
            if self.velX < max_speed:
                self.velX += self.acceleration
        if self.up_pressed:
            if self.velY > -max_speed:
                self.velY -= self.acceleration
        if self.down_pressed :
            if self.velY < max_speed:
                self.velY += self.acceleration
        
        self.x += self.velX
        self.y += self.velY
        self.velX *= self.friction
        self.velY *= self.friction

        self.rect = pygame.Rect(int(self.x),int(self.y),32,32)