Pygame曲面层：透明的精灵层问题

Question

I am drawing a small colored square, using surface.fill(color, rect) , on a sprite surface, which is then be displayed on top of the other surfaces in the following order:

1. Background surface
2. Maze surface
3. Sprite surface

Currently I am having a problem where my sprites smear across the screen because I'm not wiping the screen each time. How can I eliminate this smearing effect, while keeping the sprite layer from covering the other layers?

Layers code - Initialized, but not updated each frame.

game_surface = pygame.Surface((self.canvas.get_size()))
game_surface = game_surface.convert()
game_surface.fill((0,0,255))
maze_surface = pygame.Surface((self.canvas.get_size()))
maze_surface = maze_surface.convert_alpha()
maze_surface.fill((0,0,255,0))
play_surface = pygame.Surface((self.canvas.get_size()))
play_surface = play_surface.convert_alpha()
play_surface.fill((0,0,0,0))

Presently only the play_surface actually actually uses transparency, but eventually both the play_surface and the maze_surface will need to be transparent.

Sprites layer update - Called every time the sprite is moved.

def update(self, canvas):

    # move sprite if keys pressed (not shown)

    self.surface.fill((0,0,0,0)) # Newest screen fill attempt. Causes smearing effect
    self.surface.fill(self.color, self.rect) # draw green square
    canvas.blit(self.surface, (0,0))

Smear effect: Red = maze_layer , Green = smeared sprite Alternate sprite fill - Altered version of the above

def update(self, canvas):

    # move sprite if keys pressed (not shown)

    self.surface.fill((0,0,0)) # Original screen fill. Covers up lower layers
    self.surface.fill(self.color, self.rect) # draw green square
    canvas.blit(self.surface, (0,0))

Non-transparency - Black = filled color (I want to do this without covering up the other layers)

How can I eliminate this smearing effect (pic 1), while keeping the sprite layer from covering up the other layers (pic 2)? Any assistance is very much appreciated.

Answer 1

You need to redraw the background covered by your sprites, update their positions, and then redraw the sprites in their new position.

You may be interested in exploring the pygame.sprite module which has built-in support for this functionality. You can create subclasses of pygame.sprite.Sprite that:

1. Override the update(self) method (optional)
2. Have self.image and self.rect attributes that are used to draw them to screen
3. Are added to pygame.sprite.Group instances

Pygame's sprite group classes (such as Group , GroupSingle , LayeredUpdates , etc.) include methods like pygame.sprite.Group.clear(surface_dest, background) (see the documentation ) to facilitate the task of re-drawing background images on your sprites before moving and re-drawing them elsewhere.