PyGameExamplesAndAnswers

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Jump ‘n’ Run and Platformer

Scrolling - Center to player

Related Stack Overflow questions:

• Add scrolling to a platformer in pygame

Unfortunately, Pygame doesn’t have a built-in solution to this problem. Pygame use pygame.sprite.Sprite objects organized in pygame.sprite.Groups. The attribute .rect of the Sprites is used for drawing the objects as well as for the collision test between objects. There is no built-in feature that can convert object coordinates to screen coordinates before drawing.
As a suggestion for the developers of Pygame: It would be nice to have an optional argument for the camera offset in the method pygame.sprite.Group.draw.

There a different approaches:

• Instead of moving the player, you can move any object in the scene in the opposite direction. This is the worst of all approaches. I strongly recommend not doing this. Every time you add a new object you need to make sure that it moves as the player moves. Dealing with object animation or floating point accuracy can turn out to be a nightmare.

• Create a virtual screen size of the world and draw the entire screen on the virtual screen. At the end of each frame, a subsection of the map is displayed on the screen.

  virtual_screen = pygame.Surface((map_width, map_height))
  

  There are 2 possibilities. You can blit an area of the virtual screen directly on the screen by specifying the area argument:

  camera_area = pygame.Rect(camera_x, camera_y, camera_width, camera_height)
  screen.blit(virtual_screen, (0, 0), camera_area)
  

  The other possibility is to define a subsurface that is linked directly to the source surface using thesubsurface method:

  camera_area = pygame.Rect(camera_x, camera_y, camera_width, camera_height)
  camera_subsurf = source_surf.subsurface(camera_area)
  

  screen.blit(camera_subsurf, (0, 0))
  

  The disadvantage of this approach is that it can have a very large memory footprint. If the virtual screen is huge, the game will lag. This solution is only suitable if the size of the game area is not much larger than the screen. As a rule of thumb, if the play area is more than twice the size of the screen, you shouldn’t go this way (I’m talking about twice the size of the area, not twice the length of its width and height).

• For large play areas, the only approach that can be used is to add an offset to the objects before drawing:

  offset_x = -camera_x
  offset_y = -camera_y
  for object in objects:
      screen.blit(object.image, (object.rect.x + offset_x, object.rect.y + offset_y))
  

  Unfortunately pygame.sprite.Group.draw can not be used directly in this case. This approach is detailed in a highly rated answer.
  Alternatively, you can move all of the sprites before drawing them:

  all_sprites = pygame.sprite.Group()
  

  for sprite in all_sprites:
      all_sprites.rect.move_ip(-camera_x, -camera_y)
  all_sprites.draw(screen)    
  for sprite in all_sprites:
      all_sprites.rect.move_ip(camera_x, camera_y)
  

At the end a comment about dirty mechanisms and partial screen updates: As soon as the player moves, the entire screen is dirty and needs to be updated. It is therefore questionable whether you should invest resources in partial update mechanisms. These algorithms also take time to run. In highly dynamic scenes, the result of the algorithm is to update all.

Platform collision

Related Stack Overflow questions:

• How can I stop my player from glitching through my platform?
  

  📁 Minimal example - platform

• How to make a collision system in pygame?
  

• How to create a “Solid” block? pygame
  

• pygame platformer collision causes weird spacing issue
  

• When my player sprite runs into a wall sprite from the side, it teleports the player to the top of the wall
  

• how do I make my player collide with the bottom of my platform
  

• How to make an rectangle stay on an moving line in python
  

• Issue with Collision Detection in Pygame for simple 2D Platformer

• Is there a way to make sure a sprite collides with 2 sprites in a group?

• How to handle vector based movement and x axis tile map collisions in pygame
  

• Collision in PyGame with sprite.spritecollide and collide_rect
  

• How to overcome the problem of sprite trespassing floor due to acceleration in Pygame?

• Why is mu square not stopping at the obstacle I created?
  

• How do I make sprites in pygame not move through eachother?
  

• Falling left and right inconsistencies in pygame platformer
  

“I thought about testing if the player’s y coordinate is lower that 0, and then teleporting him to y = 0, but that feels like a really non elegant solution”

This is the usual way. The collision stops the player from falling.

“it also makes the player teleport for a frame.”

No it doesn’t. You have to “teleport” the player plyer after the collision detection and before you draw it.

You do the collision detection once in every frame. Once a collision is detected, you know that the player has hit an object at some point while moving since the last frame. Instead of calculating the exact time when the player hits the object and stopping movement, you limit the player’s position by the object.