我想知道为什么它说距离必须小于 27?为什么小于27?27从哪里来?

问题描述

我的老师给了我们这段代码来分析，我不知道他为什么把27放在那里进行碰撞.我问他他说如果玩家和敌人之间的距离小于27，我就称之为碰撞，但我还是不明白，请有人用简单的术语向我解释一下.我不明白数字 27 从何而来……当我的尺寸如此之大时?

导入数学随机导入导入pygame# 初始化pygamepygame.init()# 创建屏幕屏幕 = pygame.display.set_mode((1000, 700))# 背景background = pygame.image.load('undersea.png')# 玩家playerImg = pygame.image.load('space-invaders.png')玩家X = 500玩家Y = 600玩家X_change = 0# 敌人敌人图像 = []敌人X = []敌人Y = []敌人X_change = []敌人Y_change = []num_of_enemies = 5对于我在范围内(num_of_enemies):敌人Img.append(pygame.image.load('plastic.png'))敌人X.append(random.randint(0, 636))敌人Y.append(random.randint(50, 150))敌人X_change.append(4)敌人Y_change.append(40)#子弹# 准备好了 - 你看不到屏幕上的子弹# Fire - 子弹正在移动bulletImg = pygame.image.load('bullet (1).png')子弹X = 0子弹Y = 480子弹X_change = 0子弹Y_change = 10bullet_state =准备好"；# 分数得分值 = 0font = pygame.font.Font('freesansbold.ttf', 32)文本X = 10测试Y = 10# 游戏结束over_font = pygame.font.Font('freesansbold.ttf', 64)def show_score(x, y):score = font.render("Score: " + str(score_value), True, (255, 255, 255))screen.blit(score, (x, y))def game_over_text():over_text = over_font.render("GAME OVER", True, (255, 255, 255))screen.blit(over_text, (200, 250))定义玩家(x，y):screen.blit(playerImg, (x, y))定义敌人(x，y，i):screen.blit(enemyImg[i], (x, y))def fire_bullet(x, y):全局 bullet_state子弹状态=火"；screen.blit(bulletImg, (x + 16, y + 10))def isCollision(enemyX,enemyY,bulletX,bulletY):距离 = ((enemyX - bulletX) ** 2 + (enemyY - bulletY) ** 2)距离 = math.sqrt(距离)打印(距离)如果距离＜27:返回真别的:返回错误# 游戏循环运行 = 真在跑步的时候:# RGB = 红、绿、蓝screen.fill((0, 0, 0))# 背景图片screen.blit(背景, (0, 0))对于 pygame.event.get() 中的事件:如果 event.type == pygame.QUIT:运行 = 错误# 如果按键被按下，检查它是向右还是向左如果 event.type == pygame.KEYDOWN:如果 event.key == pygame.K_LEFT:playerX_change = -5如果 event.key == pygame.K_RIGHT:玩家X_change = 5如果 event.key == pygame.K_SPACE:如果 bullet_state 是就绪":# 获取飞船当前的x坐标子弹X = 玩家Xfire_bullet(bulletX，bulletY)如果 event.type == pygame.KEYUP:如果 event.key == pygame.K_LEFT 或 event.key == pygame.K_RIGHT:玩家X_change = 0# 5 = 5 + -0.1 ->5 = 5 - 0.1# 5 = 5 + 0.1playerX += playerX_change如果玩家X = 636:玩家X = 636# 敌人运动对于我在范围内(num_of_enemies):# 游戏结束如果敌人Y[i] >440:对于范围内的 j(num_of_enemies):敌人Y[j] = 2000game_over_text()休息敌人X[i] +=敌人X_change[i]如果敌人X[i] = 736:敌人X_change[i] = -4敌人Y[i] +=敌人Y_change[i]# 碰撞碰撞 = isCollision(enemyX[i],敌人Y[i],bulletX,bulletY)如果碰撞:子弹Y = 480bullet_state =准备好"；得分值 += 1敌人X[i] = random.randint(0, 736)敌人Y[i] = random.randint(50, 150)敌人(敌人X[i]，敌人Y[i]，我)# 子弹运动如果bulletY 

解决方案

该值为 27，因为您计算的是 函数isCollision中(enemyX,enemyY)和(bulletX,bulletY)之间的欧氏距离:

def isCollision(enemyX,enemyY,bulletX,bulletY):距离 = ((enemyX - bulletX) ** 2 + (enemyY - bulletY) ** 2)距离 = math.sqrt(距离)打印(距离)

两点(Ax, Ay)和(Bx, By)之间的欧几里得距离是

d = sqrt((Bx-Ax)**2 + (By-Ay)**2) = hypot(Bx-Ax, By-Ay)

在二维空间中，这与 勾股定理相同.边长为19的正方形对角线的长度约为27.

My teacher gave us this code to analyze and I am not sure why he put 27 there for collision.. I asked him he said if the distance between the player and the enemy is less than 27 then I will call it a collision, but I still don't understand, can someone please kindly explain it to me in simpler terms. I don't understand where the number 27 comes from.. when my dimensions are so big?

import math
import random
import pygame

# Intialize the pygame
pygame.init()

# create the screen
screen = pygame.display.set_mode((1000, 700))

# Background
background = pygame.image.load('undersea.png')


# Player
playerImg = pygame.image.load('space-invaders.png')
playerX = 500
playerY = 600
playerX_change = 0

# Enemy
enemyImg = []
enemyX = []
enemyY = []
enemyX_change = []
enemyY_change = []
num_of_enemies = 5

for i in range(num_of_enemies):
    enemyImg.append(pygame.image.load('plastic.png'))
    enemyX.append(random.randint(0, 636))
    enemyY.append(random.randint(50, 150))
    enemyX_change.append(4)
    enemyY_change.append(40)

# Bullet

# Ready - You can't see the bullet on the screen
# Fire - The bullet is currently moving

bulletImg = pygame.image.load('bullet (1).png')
bulletX = 0
bulletY = 480
bulletX_change = 0
bulletY_change = 10
bullet_state = "ready"

# Score

score_value = 0
font = pygame.font.Font('freesansbold.ttf', 32)

textX = 10
testY = 10

# Game Over
over_font = pygame.font.Font('freesansbold.ttf', 64)


def show_score(x, y):
    score = font.render("Score : " + str(score_value), True, (255, 255, 255))
    screen.blit(score, (x, y))


def game_over_text():
    over_text = over_font.render("GAME OVER", True, (255, 255, 255))
    screen.blit(over_text, (200, 250))


def player(x, y):
    screen.blit(playerImg, (x, y))


def enemy(x, y, i):
    screen.blit(enemyImg[i], (x, y))


def fire_bullet(x, y):
    global bullet_state
    bullet_state = "fire"
    screen.blit(bulletImg, (x + 16, y + 10))


def isCollision(enemyX, enemyY, bulletX, bulletY):
    distance = ((enemyX - bulletX) ** 2 + (enemyY - bulletY) ** 2)
    distance = math.sqrt(distance)
    print(distance)
    if distance < 27:
        return True
    else:
        return False


# Game Loop
running = True
while running:

    # RGB = Red, Green, Blue
    screen.fill((0, 0, 0))
    # Background Image
    screen.blit(background, (0, 0))
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

        # if keystroke is pressed check whether its right or left
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                playerX_change = -5
            if event.key == pygame.K_RIGHT:
                playerX_change = 5
            if event.key == pygame.K_SPACE:
                if bullet_state is "ready":
                    # Get the current x cordinate of the spaceship
                    bulletX = playerX
                    fire_bullet(bulletX, bulletY)

        if event.type == pygame.KEYUP:
            if event.key == pygame.K_LEFT or event.key == pygame.K_RIGHT:
                playerX_change = 0

    # 5 = 5 + -0.1 -> 5 = 5 - 0.1
    # 5 = 5 + 0.1

    playerX += playerX_change
    if playerX <= 0:
        playerX = 0
    elif playerX >= 636:
        playerX = 636

    # Enemy Movement
    for i in range(num_of_enemies):

        # Game Over
        if enemyY[i] > 440:
            for j in range(num_of_enemies):
                enemyY[j] = 2000
            game_over_text()
            break

        enemyX[i] += enemyX_change[i]
        if enemyX[i] <= 0:
            enemyX_change[i] = 4
            enemyY[i] += enemyY_change[i]
        elif enemyX[i] >= 736:
            enemyX_change[i] = -4
            enemyY[i] += enemyY_change[i]

        # Collision
        collision = isCollision(enemyX[i], enemyY[i], bulletX, bulletY)
        if collision:
            bulletY = 480
            bullet_state = "ready"
            score_value += 1
            enemyX[i] = random.randint(0, 736)
            enemyY[i] = random.randint(50, 150)

        enemy(enemyX[i], enemyY[i], i)

    # Bullet Movement
    if bulletY <= 0:
        bulletY = 480
        bullet_state = "ready"

    if bullet_state is "fire":
        fire_bullet(bulletX, bulletY)
        bulletY -= bulletY_change

    player(playerX, playerY)
    show_score(textX, testY)
    pygame.display.update()

解决方案

The value is 27, because you compute the Euclidean distance between (enemyX, enemyY) and (bulletX, bulletY) in the function isCollision:

The Euclidean distance between 2 points (Ax, Ay) and (Bx, By) is

d = sqrt((Bx-Ax)**2 + (By-Ay)**2) = hypot(Bx-Ax, By-Ay)

In 2 dimensional space this is the same as the Pythagorean theorem. The length of the diagonal in a square with a side length of 19 is approximately 27.

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