如何让敌人在pygame中跟随玩家？

Question

好的，我已经用 pygame.draw.rect 创建了一个小游戏，到目前为止，我已经创建了一个可以在屏幕上移动的玩家和一个现在什么都不做的敌人。 如果我进入一定距离（比如 100 像素）内，我希望敌人在屏幕上跟随玩家。 我将如何定义这个？ 我的玩家从 x = 300 和 y = 300 开始，敌人从 x = 500 和 y = 400 开始。

import pygame
import time
import random 
import math


pygame.init()

white = (255,255,255)
black = (0,0,0)
red = (255,0,0)
blue = (35,65,155)

gameDisplay = pygame.display.set_mode((1280,800))
pygame.display.set_caption('Practice Game')

#FPS
clock = pygame.time.Clock()
#player block size
block_size = 20

#enemy block size
block_sz = 30

enemy_x = 500
enemy_y = 400

#player health
playerHealth = 100

#Health image
healthImg = pygame.image.load('healthbarimg.png')
#enemy image
enemyImg = pygame.image.load('enemyimg.png')

font = pygame.font.SysFont(None, 25)

def player(block_size, playerList):
    for XnY in playerList:
        pygame.draw.rect(gameDisplay, black, [XnY[0],XnY[1],block_size,block_size])        

def enemy(block_sz):
    #gameDisplay.blit(enemyImg,(900,700))
    pygame.draw.rect(gameDisplay, blue,(enemy_x,enemy_y,block_sz,block_sz))

def playerHp(block_sz):
    gameDisplay.blit(healthImg,(10,10))
    gameDisplay.blit(healthImg,(45,10))
    gameDisplay.blit(healthImg,(80,10))

def message_to_screen(msg,color):
    screen_text = font.render(msg, True, color)
    gameDisplay.blit(screen_text, [450,350])

def gameLoop():
    gameExit = False
    gameOver = False

    lead_x = 300
    lead_y = 300

    enemy_x = 500
    enemy_y = 400

    enemy_x_change = 0
    enemy_y_change = 0

    lead_x_change = 0
    lead_y_change = 0

    healthList = []
    healthLength = 1

    playerList = []
    playerLength = 1

    randAppleX = round(random.randrange(0, 800-10))#/10.0)*10.0
    randAppleY = round(random.randrange(0, 800-10))#/10.0)*10.0


    while not gameExit:

        while gameOver == True:
            gameDisplay.fill(white)
            message_to_screen("Game over, press C to play again or Q to quit", red)
            pygame.display.update()

            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    gameOver = False
                    gameExit = True

                if event.type == pygame.KEYDOWN:
                    if event.key == pygame.K_q:
                        gameExit = True
                        gameOver = False
                    if event.key == pygame.K_c:
                        gameLoop()


        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                gameExit = True  
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_LEFT:
                    lead_x_change = -10
                if event.key == pygame.K_RIGHT:
                    lead_x_change = 10
                if event.key == pygame.K_UP:
                    lead_y_change = -10
                if event.key == pygame.K_DOWN:
                    lead_y_change = 10   
            if event.type == pygame.KEYUP:
                if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                    lead_x_change = 0
                if event.key == pygame.K_UP or event.key == pygame.K_DOWN:
                    lead_y_change = 0
            if lead_x >= 1280 or lead_x < 0 or lead_y >= 800 or lead_y < 0:
                gameOver = True       

            '''if enemy_x >= 900:
                enemy_x = -10 * enemySpeed                            
            if enemy_x <= 250:
                enemy_x = 10 * enemySpeed
            if enemy_y >= 700:
                enemy_y = -10 * enemySpeed
            if enemy_y <= 50:
                enemy_y = -10 * enemySpeed'''




        pygame.display.update()

        lead_x += lead_x_change
        lead_y += lead_y_change


        gameDisplay.fill(white)

        AppleThickness = 30
        pygame.draw.rect(gameDisplay, red, [randAppleX, randAppleY, AppleThickness,AppleThickness])


        playerHead = []
        playerHead.append(lead_x)
        playerHead.append(lead_y)
        playerList.append(playerHead)

        if len(playerList) > playerLength:
            del playerList[0]
        player(block_size, playerList)
        enemy(block_sz)
        playerHp(block_sz)         

        pygame.display.update()

##        if lead_x >= randAppleX and lead_x <= randAppleX + AppleThickness:
##            if lead_y >= randAppleY and lead_y <= randAppleY + AppleThickness:
##                randAppleX = round(random.randrange(0, 800-10))#/10.0)*10.0
##                randAppleY = round(random.randrange(0, 800-10))#/10.0)*10.0
##                snakeLength += 1 

        if lead_x > randAppleX and lead_x < randAppleX + AppleThickness or lead_x + block_size > randAppleX and lead_x + block_size < randAppleX + AppleThickness:
            #print("x crossover")
            if lead_y > randAppleY and lead_y < randAppleY + AppleThickness:

                randAppleX = round(random.randrange(0, 800-10))#/10.0)*10.0
                randAppleY = round(random.randrange(0, 800-10))#/10.0)*10.0
                playerLength += 1 

            elif lead_y + block_size > randAppleY and lead_y + block_size < randAppleY + AppleThickness:

                randAppleX = round(random.randrange(0, 800-10))#/10.0)*10.0
                randAppleY = round(random.randrange(0, 800-10))#/10.0)*10.0
                playerLength += 1






        clock.tick(10)

    pygame.quit()
    quit()

gameLoop()

Answer 1

首先你要解决一个问题。 变量enemy_x和enemy_y被声明了两次。 Onec 全局和一次进入gameLoop 。 保留全局变量，但删除函数中的局部变量：

enemy_x = 500
enemy_y = 400

# [...]

def gameLoop():

     global enemy_x, enemy_y

     # [...]

     # enemy_x = 500 <---- delete this
     # enemy_y = 400 <---- delete this

定义敌人和玩家之间的阈值距离，激活和停用后续并定义敌人的速度：

例如

enemySpeed = 5
min_dist = 200

要让敌人跟随玩家，您必须计算敌人与玩家之间的距离：

delta_x = lead_x - enemy_x
delta_y = lead_y - enemy_y

检查玩家是否离敌人足够近。 测试是否在两个方向（x 和 y）都低于阈值。 确定敌人沿 x 或 y 轴的步数：

if abs(delta_x) <= min_dist and abs(delta_y) <= min_dist:
    enemy_move_x = abs(delta_x) > abs(delta_y)

如果敌人在两个轴上都足够远（超过 1 步），则可以随机选择该步的轴。 请注意，这是可选的：

if abs(delta_x) > enemySpeed and abs(delta_x) > enemySpeed:
    enemy_move_x = random.random() < 0.5

与敌人迈出一步，但要限制与玩家的距离（敌人不应“跨过”玩家）：

if enemy_move_x:
    enemy_x += min(delta_x, enemySpeed) if delta_x > 0 else max(delta_x, -enemySpeed)
else:
    enemy_y += min(delta_y, enemySpeed) if delta_y > 0 else max(delta_y, -enemySpeed)

在lead_x和lead_y更新后添加代码：

enemySpeed = 5
min_dist = 200

while not gameExit:

    while gameOver == True:
        gameDisplay.fill(white)
        # [...]


    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            gameExit = True  
        # [...]


    pygame.display.update()

    lead_x += lead_x_change
    lead_y += lead_y_change

    delta_x = lead_x - enemy_x
    delta_y = lead_y - enemy_y

    if abs(delta_x) <= min_dist and abs(delta_y) <= min_dist:
        enemy_move_x = abs(delta_x) > abs(delta_y)
        if abs(delta_x) > enemySpeed and abs(delta_x) > enemySpeed:
           enemy_move_x = random.random() < 0.5
        if enemy_move_x:
           enemy_x += min(delta_x, enemySpeed) if delta_x > 0 else max(delta_x, -enemySpeed)
        else:
           enemy_y += min(delta_y, enemySpeed) if delta_y > 0 else max(delta_y, -enemySpeed)

    gameDisplay.fill(white)

    # [...]

Answer 2

你需要一个寻路。 游戏中最常用的寻路是A* 寻路。 Python中有大量的实现。

但是，A* 算法会找到到目标（即玩家）的最短路径，这可能不是必需的。 愚蠢的动作有时会给玩家时间做出反应并击退，所以只要不顾障碍地向玩家移动就足够了。 视情况而定。