与Pymunk和Pygame一起横向滚动。如何移动相机/视口以仅查看世界的一部分？

Question

从pymunk示例中，我已经看到pymunk坐标和pygame坐标之间存在差异。此外，该pymunk仅用于2D物理，而pygame用于在屏幕上渲染对象/精灵。

因此，在寻找如何建立相机跟随玩家的环境时，人们（包括我）最终会getting confused。我看过示例here，here，here和here（甚至很惊讶没有人回答this），但是给出了与反复问过同样的话题，老实说，我的回答并不能充分解释这个概念，并要求向社区展示最简单的示例，在该示例中，所有代码都带有注释。

我曾在OGRE和OSG等3D环境中工作，其中相机是可以用视锥浏览器定义的正​​确概念，但令我感到惊讶的是2D世界没有为此提供预定义功能。因此：

如果在pymunk或pygame的官方教程中没有提供，至少可以提供一个简单的示例（以pymunk身体作为玩家，世界上很少的pymunk身体）作为答案，玩家在其中移动在2D pymunk + pygame世界中，相机跟随玩家？

Answer 1

好的，我会尝试简化这个过程（我假设pygame基本知识）。

首先，让我们从一些基本的内容开始。您可以环游世界的小精灵：

import pygame
import random

class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = pygame.Surface((32, 32))
        self.image.fill(pygame.Color('dodgerblue'))
        self.rect = self.image.get_rect()
        self.pos = pygame.Vector2((100, 200))

    def update(self, events, dt):
        pressed = pygame.key.get_pressed()
        move = pygame.Vector2((0, 0))
        if pressed[pygame.K_w]: move += (0, -1)
        if pressed[pygame.K_a]: move += (-1, 0)
        if pressed[pygame.K_s]: move += (0, 1)
        if pressed[pygame.K_d]: move += (1, 0)
        if move.length() > 0: move.normalize_ip()
        self.pos += move*(dt/5)
        self.rect.center = self.pos

def main():
    pygame.init()
    screen = pygame.display.set_mode((500, 500))
    clock = pygame.time.Clock()
    dt = 0
    player = Player()
    sprites = pygame.sprite.Group(player)
    background = screen.copy()
    background.fill((30, 30, 30))
    for _ in range(1000):
        x, y = random.randint(0, 1000), random.randint(0, 1000)
        pygame.draw.rect(background, pygame.Color('green'), (x, y, 2, 2))

    while True:
        events = pygame.event.get()
        for e in events:
            if e.type == pygame.QUIT:
                return
        sprites.update(events, dt)
        screen.blit(background, (0, 0))
        sprites.draw(screen)
        pygame.display.update()
        dt = clock.tick(60)

if __name__ == '__main__':
    main()

到目前为止，还没有疯狂。

---

那么，什么是“相机”？这只是一个x和一个y值，我们使用它来移动整个“世界”（例如不是UI的所有内容）。这是我们游戏对象的坐标与屏幕之间的抽象。

在上面的示例中，当要在位置(x, y)上绘制游戏对象（玩家或背景）时，我们在此位置的屏幕上绘制它们。

现在，如果我们要在“摄像机”周围移动，我们只需创建另一个x, y对，并将其添加到游戏对象的坐标即可确定屏幕上的实际位置。我们开始区分世界坐标（游戏逻辑认为对象的位置在哪里）和屏幕坐标（实际）对象在屏幕上的位置。

这是我们带有“ camera”（带引号的“ camera”）的示例，因为它实际上只是两个值：

import pygame
import random

class Player(pygame.sprite.Sprite):
    def __init__(self):
        super().__init__()
        self.image = pygame.Surface((32, 32))
        self.image.fill(pygame.Color('dodgerblue'))
        self.rect = self.image.get_rect()
        self.pos = pygame.Vector2((100, 200))

    def update(self, events, dt):
        pressed = pygame.key.get_pressed()
        move = pygame.Vector2((0, 0))
        if pressed[pygame.K_w]: move += (0, -1)
        if pressed[pygame.K_a]: move += (-1, 0)
        if pressed[pygame.K_s]: move += (0, 1)
        if pressed[pygame.K_d]: move += (1, 0)
        if move.length() > 0: move.normalize_ip()
        self.pos += move*(dt/5)
        self.rect.center = self.pos

def main():
    pygame.init()
    screen = pygame.display.set_mode((500, 500))
    clock = pygame.time.Clock()
    dt = 0
    player = Player()
    sprites = pygame.sprite.Group(player)
    # the "world" is now bigger than the screen
    # so we actually have anything to move the camera to
    background = pygame.Surface((1500, 1500))
    background.fill((30, 30, 30))

    # a camera is just two values: x and y
    # we use a vector here because it's easier to handle than a tuple
    camera = pygame.Vector2((0, 0))

    for _ in range(3000):
        x, y = random.randint(0, 1000), random.randint(0, 1000)
        pygame.draw.rect(background, pygame.Color('green'), (x, y, 2, 2))

    while True:
        events = pygame.event.get()
        for e in events:
            if e.type == pygame.QUIT:
                return

        # copy/paste because I'm lazy
        # just move the camera around
        pressed = pygame.key.get_pressed()
        camera_move = pygame.Vector2()
        if pressed[pygame.K_UP]: camera_move += (0, 1)
        if pressed[pygame.K_LEFT]: camera_move += (1, 0)
        if pressed[pygame.K_DOWN]: camera_move += (0, -1)
        if pressed[pygame.K_RIGHT]: camera_move += (-1, 0)
        if camera_move.length() > 0: camera_move.normalize_ip()
        camera += camera_move*(dt/5)

        sprites.update(events, dt)

        # before drawing, we shift everything by the camera's x and y values
        screen.blit(background, camera)
        for s in sprites:
            screen.blit(s.image, s.rect.move(*camera))

        pygame.display.update()
        dt = clock.tick(60)

if __name__ == '__main__':
    main()

现在您可以使用箭头键移动摄像机。

就是这样。我们只是将所有内容移动一点，然后将其发送到屏幕。

有关完整示例（支持精灵，停在世界边缘，平稳移动），请参阅此question。

---

对于使用pymunk而言：它确实有效。由于它可以与世界坐标一起使用，而不是与屏幕坐标一起使用，因此它不会受到绘制内容到其他位置的影响。唯一的陷阱是，与pygame的y轴相比，pymunk的y轴发生了翻转，但是您可能已经知道了。

这是一个例子：

import pygame
import random
import pymunk

class Player(pygame.sprite.Sprite):
    def __init__(self, space):
        super().__init__()
        self.space = space
        self.image = pygame.Surface((32, 32))
        self.image.fill(pygame.Color('dodgerblue'))
        self.rect = self.image.get_rect()
        self.pos = pygame.Vector2((100, 200))
        self.body = pymunk.Body(1,1666)
        self.body.position = self.pos
        self.poly = pymunk.Poly.create_box(self.body)
        self.space.add(self.body, self.poly)

    def update(self, events, dt):
        pressed = pygame.key.get_pressed()
        move = pygame.Vector2((0, 0))
        if pressed[pygame.K_w]: move += (0, 1)
        if pressed[pygame.K_a]: move += (-1, 0)
        if pressed[pygame.K_s]: move += (0, -1)
        if pressed[pygame.K_d]: move += (1, 0)
        if move.length() > 0: move.normalize_ip()
        self.body.apply_impulse_at_local_point(move*5)

        # if you used pymunk before, you'll probably already know
        # that you'll have to invert the y-axis to convert between
        # the pymunk and the pygame coordinates.
        self.pos = pygame.Vector2(self.body.position[0], -self.body.position[1]+500)
        self.rect.center = self.pos

def main():
    pygame.init()
    screen = pygame.display.set_mode((500, 500))
    clock = pygame.time.Clock()
    dt = 0

    space = pymunk.Space()
    space.gravity = 0,-100

    player = Player(space)
    sprites = pygame.sprite.Group(player)

    # the "world" is now bigger than the screen
    # so we actually have anything to move the camera to
    background = pygame.Surface((1500, 1500))
    background.fill((30, 30, 30))

    # a camera is just two values: x and y
    # we use a vector here because it's easier to handle than a tuple
    camera = pygame.Vector2((0, 0))

    for _ in range(3000):
        x, y = random.randint(0, 1000), random.randint(0, 1000)
        pygame.draw.rect(background, pygame.Color('green'), (x, y, 2, 2))

    while True:
        events = pygame.event.get()
        for e in events:
            if e.type == pygame.QUIT:
                return

        # copy/paste because I'm lazy
        # just move the camera around
        pressed = pygame.key.get_pressed()
        camera_move = pygame.Vector2()
        if pressed[pygame.K_UP]: camera_move += (0, 1)
        if pressed[pygame.K_LEFT]: camera_move += (1, 0)
        if pressed[pygame.K_DOWN]: camera_move += (0, -1)
        if pressed[pygame.K_RIGHT]: camera_move += (-1, 0)
        if camera_move.length() > 0: camera_move.normalize_ip()
        camera += camera_move*(dt/5)

        sprites.update(events, dt)

        # before drawing, we shift everything by the camera's x and y values
        screen.blit(background, camera)
        for s in sprites:
            screen.blit(s.image, s.rect.move(*camera))

        pygame.display.update()
        dt = clock.tick(60)
        space.step(dt/1000)

if __name__ == '__main__':
    main()

---

请注意，当您使用pymunk.Space.debug_draw时，将无法将世界坐标转换为屏幕坐标，因此最好将pymunk内容绘制到另一个Surface，然后< em> translate Surface。

这是带有移动相机的pymunk的pygame_util_demo.py：

import sys

import pygame
from pygame.locals import *

import pymunk
from pymunk.vec2d import Vec2d
import pymunk.pygame_util

import shapes_for_draw_demos

def main():
    pygame.init()
    screen = pygame.display.set_mode((1000,700)) 
    pymunk_layer = pygame.Surface((1000,700))
    pymunk_layer.set_colorkey((12,12,12))
    pymunk_layer.fill((12,12,12))
    camera = pygame.Vector2((0, 0))
    clock = pygame.time.Clock()
    font = pygame.font.SysFont("Arial", 16)

    space = pymunk.Space()

    captions = shapes_for_draw_demos.fill_space(space)

    # Info
    color = pygame.color.THECOLORS["black"]

    options = pymunk.pygame_util.DrawOptions(pymunk_layer)

    while True:
        for event in pygame.event.get():
            if event.type == QUIT or \
                event.type == KEYDOWN and (event.key in [K_ESCAPE, K_q]):  
                return 
            elif event.type == KEYDOWN and event.key == K_p:
                pygame.image.save(screen, "pygame_util_demo.png")                

        # copy/paste because I'm lazy
        pressed = pygame.key.get_pressed()
        camera_move = pygame.Vector2()
        if pressed[pygame.K_UP]: camera_move += (0, 1)
        if pressed[pygame.K_LEFT]: camera_move += (1, 0)
        if pressed[pygame.K_DOWN]: camera_move += (0, -1)
        if pressed[pygame.K_RIGHT]: camera_move += (-1, 0)
        if camera_move.length() > 0: camera_move.normalize_ip()
        camera += camera_move*5

        screen.fill(pygame.color.THECOLORS["white"])
        pymunk_layer.fill((12,12,12))
        space.debug_draw(options)
        screen.blit(pymunk_layer, camera)
        screen.blit(font.render("Demo example of pygame_util.DrawOptions()", 1, color), (205, 680))
        for caption in captions:
            x, y = caption[0]
            y = 700 - y
            screen.blit(font.render(caption[1], 1, color), camera + (x,y))
        pygame.display.flip()

        clock.tick(30)

if __name__ == '__main__':
    sys.exit(main())