Move with a Scrolling Screen - Centered#
Using a arcade.Camera, a program can easily scroll around a larger
“world” while only showing part of it on the screen.
If you are displaying a GUI or some other items that should NOT scroll, you’ll need two cameras. One that shows the unscrolled GUI, and one that shows the scrolled sprites.
See also Move with a Scrolling Screen - Margins.
sprite_move_scrolling.py#
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Scroll around a large screen.
Artwork from https://kenney.nl
If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.sprite_move_scrolling
"""
import random
import arcade
from pyglet.math import Vec2
SPRITE_SCALING = 0.5
DEFAULT_SCREEN_WIDTH = 800
DEFAULT_SCREEN_HEIGHT = 600
SCREEN_TITLE = "Sprite Move with Scrolling Screen Example"
# How many pixels to keep as a minimum margin between the character
# and the edge of the screen.
VIEWPORT_MARGIN = 220
# How fast the camera pans to the player. 1.0 is instant.
CAMERA_SPEED = 0.1
# How fast the character moves
PLAYER_MOVEMENT_SPEED = 7
class MyGame(arcade.Window):
""" Main application class. """
def __init__(self, width, height, title):
"""
Initializer
"""
super().__init__(width, height, title, resizable=True)
# Sprite lists
self.player_list = None
self.wall_list = None
# Set up the player
self.player_sprite = None
# Physics engine so we don't run into walls.
self.physics_engine = None
# Track the current state of what key is pressed
self.left_pressed = False
self.right_pressed = False
self.up_pressed = False
self.down_pressed = False
# Create the cameras. One for the GUI, one for the sprites.
# We scroll the 'sprite world' but not the GUI.
self.camera_sprites = arcade.Camera(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT)
self.camera_gui = arcade.Camera(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT)
def setup(self):
""" Set up the game and initialize the variables. """
# Sprite lists
self.player_list = arcade.SpriteList()
self.wall_list = arcade.SpriteList()
# Set up the player
self.player_sprite = arcade.Sprite(":resources:images/animated_characters/female_person/femalePerson_idle.png",
scale=0.4)
self.player_sprite.center_x = 256
self.player_sprite.center_y = 512
self.player_list.append(self.player_sprite)
# -- Set up several columns of walls
for x in range(200, 1650, 210):
for y in range(0, 1600, 64):
# Randomly skip a box so the player can find a way through
if random.randrange(5) > 0:
wall = arcade.Sprite(":resources:images/tiles/grassCenter.png", SPRITE_SCALING)
wall.center_x = x
wall.center_y = y
self.wall_list.append(wall)
self.physics_engine = arcade.PhysicsEngineSimple(self.player_sprite, self.wall_list)
# Set the background color
arcade.set_background_color(arcade.color.AMAZON)
def on_draw(self):
""" Render the screen. """
# This command has to happen before we start drawing
self.clear()
# Select the camera we'll use to draw all our sprites
self.camera_sprites.use()
# Draw all the sprites.
self.wall_list.draw()
self.player_list.draw()
# Select the (unscrolled) camera for our GUI
self.camera_gui.use()
# Draw the GUI
arcade.draw_rectangle_filled(self.width // 2,
20,
self.width,
40,
arcade.color.ALMOND)
text = f"Scroll value: ({self.camera_sprites.position[0]:5.1f}, " \
f"{self.camera_sprites.position[1]:5.1f})"
arcade.draw_text(text, 10, 10, arcade.color.BLACK_BEAN, 20)
def on_key_press(self, key, modifiers):
"""Called whenever a key is pressed. """
if key == arcade.key.UP:
self.up_pressed = True
elif key == arcade.key.DOWN:
self.down_pressed = True
elif key == arcade.key.LEFT:
self.left_pressed = True
elif key == arcade.key.RIGHT:
self.right_pressed = True
def on_key_release(self, key, modifiers):
"""Called when the user releases a key. """
if key == arcade.key.UP:
self.up_pressed = False
elif key == arcade.key.DOWN:
self.down_pressed = False
elif key == arcade.key.LEFT:
self.left_pressed = False
elif key == arcade.key.RIGHT:
self.right_pressed = False
def on_update(self, delta_time):
""" Movement and game logic """
# Calculate speed based on the keys pressed
self.player_sprite.change_x = 0
self.player_sprite.change_y = 0
if self.up_pressed and not self.down_pressed:
self.player_sprite.change_y = PLAYER_MOVEMENT_SPEED
elif self.down_pressed and not self.up_pressed:
self.player_sprite.change_y = -PLAYER_MOVEMENT_SPEED
if self.left_pressed and not self.right_pressed:
self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED
elif self.right_pressed and not self.left_pressed:
self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED
# Call update on all sprites (The sprites don't do much in this
# example though.)
self.physics_engine.update()
# Scroll the screen to the player
self.scroll_to_player()
def scroll_to_player(self):
"""
Scroll the window to the player.
if CAMERA_SPEED is 1, the camera will immediately move to the desired position.
Anything between 0 and 1 will have the camera move to the location with a smoother
pan.
"""
position = Vec2(self.player_sprite.center_x - self.width / 2,
self.player_sprite.center_y - self.height / 2)
self.camera_sprites.move_to(position, CAMERA_SPEED)
def on_resize(self, width, height):
"""
Resize window
Handle the user grabbing the edge and resizing the window.
"""
self.camera_sprites.resize(int(width), int(height))
self.camera_gui.resize(int(width), int(height))
def main():
""" Main function """
window = MyGame(DEFAULT_SCREEN_WIDTH, DEFAULT_SCREEN_HEIGHT, SCREEN_TITLE)
window.setup()
arcade.run()
if __name__ == "__main__":
main()
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