python - Pygame:无限滚动相机？

Question

所以我在 pygame 中编写了一个小型平台游戏，您可以在其中放置方 block 并在它们上面跳来跳去……但是，游戏仅限于窗口的边界(很明显)。那么如何添加一种使用 A 和 D 键滚动“相机”的方法呢？

这是游戏的代码:

    import pygame,random
    from pygame.locals import *
    from collections import namedtuple

    pygame.init()
    clock=pygame.time.Clock()
    screen=pygame.display.set_mode((640,480))
    pygame.display.set_caption("PiBlocks | By Sam Tubb")
    max_gravity = 100
    blocksel="texture\\dirt.png"
    curs = pygame.image.load("texture\\cursor.png").convert()
    curs.set_colorkey((0,255,0))

    class Block(object):
            def __init__(self,x,y,sprite):
                    self.sprite = pygame.image.load(sprite).convert_alpha()
                    self.rect = self.sprite.get_rect(centery=y, centerx=x)

    class Player(object):
        sprite = pygame.image.load("texture\\playr.png").convert()
        sprite.set_colorkey((0,255,0))
        def __init__(self, x, y):
            self.rect = self.sprite.get_rect(centery=y, centerx=x)
            # indicates that we are standing on the ground
            # and thus are "allowed" to jump
            self.on_ground = True
            self.xvel = 0
            self.yvel = 0
            self.jump_speed = 7
            self.move_speed = 3

        def update(self, move, blocks):

            # check if we can jump 
            if move.up and self.on_ground: 
                self.yvel -= self.jump_speed

            # simple left/right movement
            if move.left: self.xvel = -self.move_speed
            if move.right: self.xvel = self.move_speed

            # if in the air, fall down
            if not self.on_ground:
                self.yvel += 0.3
                # but not too fast
                if self.yvel > max_gravity: self.yvel = max_gravity

            # if no left/right movement, x speed is 0, of course
            if not (move.left or move.right):
                self.xvel = 0

            # move horizontal, and check for horizontal collisions
            self.rect.left += self.xvel
            self.collide(self.xvel, 0, blocks)

            # move vertically, and check for vertical collisions
            self.rect.top += self.yvel
            self.on_ground = False;
            self.collide(0, self.yvel, blocks)

        def collide(self, xvel, yvel, blocks):
            # all blocks that we collide with
            for block in [blocks[i] for i in self.rect.collidelistall(blocks)]:

                # if xvel is > 0, we know our right side bumped 
                # into the left side of a block etc.
                if xvel > 0: self.rect.right = block.rect.left
                if xvel < 0: self.rect.left = block.rect.right

                # if yvel > 0, we are falling, so if a collision happpens 
                # we know we hit the ground (remember, we seperated checking for
                # horizontal and vertical collision, so if yvel != 0, xvel is 0)
                if yvel > 0:
                    self.rect.bottom = block.rect.top
                    self.on_ground = True
                    self.yvel = 0
                # if yvel < 0 and a collision occurs, we bumped our head
                # on a block above us
                if yvel < 0: self.rect.top = block.rect.bottom

    colliding = False
    Move = namedtuple('Move', ['up', 'left', 'right'])
    player=[]
    blocklist=[]
    font=pygame.font.Font(None,20)
    while True:
        screen.fill((25,30,90))
        mse = pygame.mouse.get_pos()
        key = pygame.key.get_pressed()
        if key[K_1]:
            blocksel="texture\\dirt.png"
        if key[K_2]:
            blocksel="texture\\stonetile.png"
        if key[K_3]:
            blocksel="texture\\sand.png"
        if key[K_ESCAPE]:
            exit()
        for event in pygame.event.get():
            if event.type == QUIT:
                exit()

            if key[K_LSHIFT]:
                if event.type==MOUSEMOTION:
                    if not any(block.rect.collidepoint(mse) for block in blocklist):
                        x=(int(mse[0]) / 32)*32
                        y=(int(mse[1]) / 32)*32
                        blocklist.append(Block(x+16,y+16,blocksel))
            else:
                if event.type == pygame.MOUSEBUTTONUP:
                    if event.button == 1:
                        to_remove = [b for b in blocklist if b.rect.collidepoint(mse)]
                        for b in to_remove:
                            blocklist.remove(b)

                        if not to_remove:
                            x=(int(mse[0]) / 32)*32
                            y=(int(mse[1]) / 32)*32
                            blocklist.append(Block(x+16,y+16,blocksel))

                    elif event.button == 3:
                        x=(int(mse[0]) / 32)*32
                        y=(int(mse[1]) / 32)*32
                        player=Player(x+16,y+16)

        move = Move(key[K_UP], key[K_LEFT], key[K_RIGHT])

        for b in blocklist:
                screen.blit(b.sprite, b.rect)

        if player:
            player.update(move, blocklist)
            screen.blit(player.sprite, player.rect)
        x=(int(mse[0]) / 32)*32
        y=(int(mse[1]) / 32)*32
        screen.blit(curs,(x,y))
        clock.tick(60)
        x=blocksel.replace('texture\\','')
        x=x.replace('.png','')
        words=font.render('Selected Block: '+str(x), True, (255,255,255))
        screen.blit(words,(1,1))
        pygame.display.flip()

感谢任何帮助:)

Answer 1

为了拥有滚动相机，您必须区分屏幕坐标和世界坐标。

在此图中，屏幕的轮廓(和屏幕坐标)以红色显示。世界坐标为黑色。虚线箭头显示屏幕原点与世界原点(相机矢量 或相机位置)的偏移量。

在绘制对象时，您需要将世界坐标转换为屏幕坐标(相机变换)，然后将屏幕坐标转换回世界坐标(逆相机变换) em>) 在确定鼠标指向哪个 block 时。

在 2-D 中，这些变换很简单:相机变换是“世界坐标减去相机位置”，逆相机变换是“屏幕坐标加上相机位置”。

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如果您对代码的更一般性评论感兴趣，您可以考虑将您的代码发布到 Code Review (当你觉得它尽可能好时)。

关于我发现的问题的一些快速说明:

1. 每次创建新 block 时加载纹理并制作 Sprite 。这似乎有点浪费:为什么不只加载每个纹理一次并多次使用 Sprite ？

2. 玩家无法控制跳跃的高度。值得仔细研究 super 马里奥世界等经典平台游戏，了解跳跃的原理。

3. 速度以每帧像素表示，这意味着您不能改变帧率。考虑以每秒像素数表示速度并乘以时间步长。

4. 变量 max_gravity 命名不当:它是玩家的终端向下速度。 (此外，由于它是常量，您可能希望将其命名为大写。)

5. 有很多重复的代码可以转化为函数或方法。例如，这样的代码:

   x=(int(mse[0]) / 32)*32
   y=(int(mse[1]) / 32)*32
   ... x+16,y+16 ...
   

   出现在四个地方。 (当您修改代码以添加相机位置时，这将成为逆相机变换。)

6. 如果您为常量命名，代码将更易于理解，例如:

   BACKGROUND_COLOR = 25, 30, 90
   TEXT_COLOR = pygame.Color('white')
   BLOCK_SIZE = 32, 32
   SCREEN_SIZE = 640, 480
   FRAMES_PER_SECOND = 60