Python（Pygame） - 以不同速度向背景移動的對象實例

Question

這一直在我的腦海中持續數日。我正在嘗試創建一個遊戲，遊戲中有一個固定在中間的玩家，以及一個基於瓦片的背景，在玩家身後流暢地移動，並在玩家移動時生成額外的瓦片圖像。背景完美到目前爲止。

當我嘗試將對象添加到背景（例如樹）時，會出現此問題。我希望這個對象保持固定在某個背景位置，但隨着玩家的移動，對象逐漸相對於背景移動。也就是說，物體會隨着玩家的移動而移動（因爲它應該），但它也會移動太多。

我已經隔離了World.update方法的原因，self.tileShift部分。如果你刪除了整個if/elif部分，這個行爲看起來不錯（當然背景沒有正確更新，所以我們需要這個部分）。不知何故，當tileShift跳過時，屏幕上的每個對象也會跳過幾個像素。花了一週的研究和試驗後，我仍然無法解決它。我試圖改變圖像，改變tileShift截點，改變調用更新/繪製方法的順序等。

請參考下面的代碼（從原始的，但自包含的代碼大量剝離下來）。請注意，我們需要一個帶有模式的背景平鋪圖像（請參閱World class init），否則您將無法看到我描述的行爲，因爲錯誤的移動是如此漸進的。爲獲得最佳性能，請使用70x70 png圖像。

希望這個解釋是有道理的，請讓我知道是否需要任何額外的信息。任何幫助將不勝感激！！

import pygame 

# Initialisation 
SCREEN_WIDTH, SCREEN_HEIGHT = 800, 850 
pygame.init() # Initialise pygame 
window = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT)) # Set the window surface (the main screen of the game) 
pygame.display.set_caption("Game") # Game window caption 
window_rect = window.get_rect() 

# GLOBAL VARIABLES 
WorldMove = dict(x=0, y=0) # List for the direction and amount the background moves as the player moves 
PlayerMoveSpeed = 5 

# CLASSES 
class World(pygame.sprite.Sprite): 
    def __init__(self): 
     self.tileShift = dict(x=0, y=0) # Tracker for when the player has passed from one map tile to another 

     # Load and set up the tile images 
     self.tiles = pygame.image.load("Images\Tiles\Tile.png") 
     self.tileSize = self.tiles.get_rect().size[0] # Assumes a square size 
     self.map = pygame.Surface((self.tileSize*14,self.tileSize*15)) # Visible area surface size, based on tile size 
     self.rect = self.map.get_rect() # Create a rect attribute for the World, so it can be blitted to the window 
     self.rect.x, self.rect.y = -self.tileSize,-self.tileSize # The map is blitted starting one tile size above left of the screen (so we see no whitespace) 

    def update(self): 
     # Move the map around the player based on WorldMove, which is set in the player_move function 
     self.rect.x += WorldMove["x"] 
     self.rect.y += WorldMove["y"] 

     # Update the tileShift based on player movement so we know when they've moved onto another tile 
     if WorldMove["x"] != 0: self.tileShift["x"] -= WorldMove["x"] 
     if WorldMove["y"] != 0: self.tileShift["y"] -= WorldMove["y"] 

     # Once the self.tileShift has passed the size of one of the tile images, reset it and move self.matrix by 1 
     if self.tileShift["x"] < -self.tileSize: 
      self.tileShift["x"] = 0 # Reset the tileShift variable 
      self.rect.x = -self.tileSize # Reset the point from which the map is blitted to window to top left of visible screen 
     elif self.tileShift["x"] > self.tileSize: 
      self.tileShift["x"] = 0 
      self.rect.x = -self.tileSize 
     if self.tileShift["y"] > self.tileSize: 
      self.tileShift["y"] = 0 
      self.rect.y = -self.tileSize 
     elif self.tileShift["y"] < -self.tileSize: 
      self.tileShift["y"] = 0 
      self.rect.y = -self.tileSize 

    def draw(self): 
     # Draw the tiles in a grid in the visible area 
     for y in range(15): # Visible number of tiles on y axis 
      for x in range(14): # Visible number of tiles on x axis 
       self.map.blit(self.tiles, (self.tileSize*x, self.tileSize*y)) # Blit each tile onto self.map 
     window.blit(self.map, self.rect) # Blit self.map onto the window 

class Player(pygame.sprite.Sprite): 
    def __init__(self): 
     self.image = pygame.Surface((35, 35)) 
     self.image.fill((0, 0, 0)) 
     self.rect = (SCREEN_WIDTH/2, SCREEN_HEIGHT/2) # Player is always in middle of screen 

    def player_move(self): 
     global WorldMove # Make sure that we're referring to and updating the global variable for the world movement 

     key = pygame.key.get_pressed() 
     x, y = 0, 0 

     if key[pygame.K_w] or key[pygame.K_UP]: y = PlayerMoveSpeed 
     if key[pygame.K_d] or key[pygame.K_RIGHT]: x = -PlayerMoveSpeed 
     if key[pygame.K_a] or key[pygame.K_LEFT]: x = PlayerMoveSpeed 
     if key[pygame.K_s] or key[pygame.K_DOWN]: y = -PlayerMoveSpeed 

     if x != 0 and y != 0: # If more than one key pressed, move diagonally 
      WorldMove["x"] = int(x/1.5) 
      WorldMove["y"] = int(y/1.5) 
     else: 
      WorldMove["x"] = x 
      WorldMove["y"] = y 

    def draw(self): 
     window.blit(self.image, self.rect) 

class Object(pygame.sprite.Sprite): 

    def __init__(self): 
     self.image = pygame.Surface((50,100)) 
     self.image.fill((50,50,250)) 
     self.rect = self.image.get_rect() 
     self.rect.center = window_rect.center 
     self.rect.x, self.rect.y = 100, 100 # Spawn location of the object 

    def update(self): # Move the object as the world moves around the player 
     self.rect.x += WorldMove["x"] 
     self.rect.y += WorldMove["y"] 

    def draw(self): # Blit the object onto the screen at its location 
     window.blit(self.image, self.rect) 

# Set Objects 
world = World() 
object = Object() 
player = Player() 

# Main Loop 
gameRunning = True 

while gameRunning: 

    # Player events 
    for event in pygame.event.get(): 

     if event.type == pygame.QUIT or (event.type == pygame.KEYDOWN and event.key == pygame.K_ESCAPE): 
      gameRunning = False 

     player.player_move() # Move player based on movement key(s) pressed (if any) 

    # Class updates and drawing to the screen 
    window.fill((255, 255, 255)) # Fill the window with background white 
    world.update() 
    world.draw() 
    object.update() 
    object.draw() 
    player.draw() 

    pygame.display.update() # Refresh the display 

# End - only reaches this point if gameRunning = False 
pygame.quit() 

Answer 1

取而代之的是World實例的self.rect設置爲-self.tileSize的，輸入或遞減RECT屬性和self.tileShift由self.tileSize：

if self.tileShift["x"] < -self.tileSize: 
    self.tileShift["x"] += self.tileSize 
    self.rect.x -= self.tileSize 
elif self.tileShift["x"] > self.tileSize: 
    self.tileShift["x"] -= self.tileSize 
    self.rect.x += self.tileSize 
if self.tileShift["y"] > self.tileSize: 
    self.tileShift["y"] -= self.tileSize 
    self.rect.y += self.tileSize 
elif self.tileShift["y"] < -self.tileSize: 
    self.tileShift["y"] += self.tileSize 
    self.rect.y -= self.tileSize