Step 6 - Add a Camera#
We can have our window be a small viewport into a much larger world by adding a camera to it.
First we need to create a new variable in our __init__
method:
# A Camera that can be used for scrolling the screen
self.camera = None
Next we can initialize the camera in the setup
function:
# Set up the Camera
self.camera = arcade.Camera(self.width, self.height)
Then to use our camera when drawing, we can activate it in our on_draw
function:
# Activate our Camera
self.camera.use()
Now at this point everything should be working the same, but the camera can do a lot
more than this. We can use the move
function of the camera to scroll it to a different
position. We can use this functionality to keep the camera centered on the player:
We can create a function to calculate the coordinates for the center of our player
relative to the screen, then move the camera to those. Then we can call that function in
on_update
to actually move it. The new position will be taken into account during
the use
function in on_draw
def center_camera_to_player(self):
screen_center_x = self.player_sprite.center_x - (self.camera.viewport_width / 2)
screen_center_y = self.player_sprite.center_y - (
self.camera.viewport_height / 2
)
# Don't let camera travel past 0
if screen_center_x < 0:
screen_center_x = 0
if screen_center_y < 0:
screen_center_y = 0
player_centered = screen_center_x, screen_center_y
self.camera.move_to(player_centered)
def on_update(self, delta_time):
"""Movement and game logic"""
# Move the player with the physics engine
self.physics_engine.update()
# Position the camera
self.center_camera_to_player()
Source Code#
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 | """ Platformer Game """ import arcade # Constants SCREEN_WIDTH = 1000 SCREEN_HEIGHT = 650 SCREEN_TITLE = "Platformer" # Constants used to scale our sprites from their original size CHARACTER_SCALING = 1 TILE_SCALING = 0.5 # Movement speed of player, in pixels per frame PLAYER_MOVEMENT_SPEED = 5 GRAVITY = 1 PLAYER_JUMP_SPEED = 20 class MyGame(arcade.Window): """ Main application class. """ def __init__(self): # Call the parent class and set up the window super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE) # Our Scene Object self.scene = None # Separate variable that holds the player sprite self.player_sprite = None # Our physics engine self.physics_engine = None # A Camera that can be used for scrolling the screen self.camera = None arcade.set_background_color(arcade.csscolor.CORNFLOWER_BLUE) def setup(self): """Set up the game here. Call this function to restart the game.""" # Set up the Camera self.camera = arcade.Camera(self.width, self.height) # Initialize Scene self.scene = arcade.Scene() # Create the Sprite lists self.scene.add_sprite_list("Player") self.scene.add_sprite_list("Walls", use_spatial_hash=True) # Set up the player, specifically placing it at these coordinates. image_source = ":resources:images/animated_characters/female_adventurer/femaleAdventurer_idle.png" self.player_sprite = arcade.Sprite(image_source, CHARACTER_SCALING) self.player_sprite.center_x = 64 self.player_sprite.center_y = 96 self.scene.add_sprite("Player", self.player_sprite) # Create the ground # This shows using a loop to place multiple sprites horizontally for x in range(0, 1250, 64): wall = arcade.Sprite(":resources:images/tiles/grassMid.png", TILE_SCALING) wall.center_x = x wall.center_y = 32 self.scene.add_sprite("Walls", wall) # Put some crates on the ground # This shows using a coordinate list to place sprites coordinate_list = [[512, 96], [256, 96], [768, 96]] for coordinate in coordinate_list: # Add a crate on the ground wall = arcade.Sprite( ":resources:images/tiles/boxCrate_double.png", TILE_SCALING ) wall.position = coordinate self.scene.add_sprite("Walls", wall) # Create the 'physics engine' self.physics_engine = arcade.PhysicsEnginePlatformer( self.player_sprite, gravity_constant=GRAVITY, walls=self.scene["Walls"] ) def on_draw(self): """Render the screen.""" # Clear the screen to the background color self.clear() # Activate our Camera self.camera.use() # Draw our Scene self.scene.draw() def on_key_press(self, key, modifiers): """Called whenever a key is pressed.""" if key == arcade.key.UP or key == arcade.key.W: if self.physics_engine.can_jump(): self.player_sprite.change_y = PLAYER_JUMP_SPEED elif key == arcade.key.LEFT or key == arcade.key.A: self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED elif key == arcade.key.RIGHT or key == arcade.key.D: self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED def on_key_release(self, key, modifiers): """Called when the user releases a key.""" if key == arcade.key.LEFT or key == arcade.key.A: self.player_sprite.change_x = 0 elif key == arcade.key.RIGHT or key == arcade.key.D: self.player_sprite.change_x = 0 def center_camera_to_player(self): screen_center_x = self.player_sprite.center_x - (self.camera.viewport_width / 2) screen_center_y = self.player_sprite.center_y - ( self.camera.viewport_height / 2 ) # Don't let camera travel past 0 if screen_center_x < 0: screen_center_x = 0 if screen_center_y < 0: screen_center_y = 0 player_centered = screen_center_x, screen_center_y self.camera.move_to(player_centered) def on_update(self, delta_time): """Movement and game logic""" # Move the player with the physics engine self.physics_engine.update() # Position the camera self.center_camera_to_player() def main(): """Main function""" window = MyGame() window.setup() arcade.run() if __name__ == "__main__": main() |