Bloom-Effect Defender#
Creating a “glowing” effect can enhance 2D games. This example shows how to do it.
Create Frame Buffer and Post-Processor#
Lines 176-202
Here we create the frame buffer, and add a color attachment to store the pixel data into.
It also creates a post-processor that will do a gaussian blur on what is rendered. There are a lot of parameters to the blur, depending on how you want it to look.
Render To Framebuffer#
Lines 239-252
When we draw, we render the objects we want to be blurred to our frame buffer, then run the post-processor to do the blur.
Note: This buffer is not transparent! Anything behind it will be hidden. So multiple layers of glow are not possible at this time, nor can you put anything ‘behind’ the glow.
Render Framebuffer To Screen#
Lines 264-265
Finally we render that buffer to the screen.
mini_map_defender.py#
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Defender Clone.
This example shows how to create a 'bloom' or 'glow' effect.
If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.experimental.bloom_defender
"""
import arcade
import os
import random
# --- Bloom related ---
from arcade.experimental import postprocessing
# Size/title of the window
SCREEN_WIDTH = 1280
SCREEN_HEIGHT = 720
SCREEN_TITLE = "Defender Clone"
# Size of the playing field
PLAYING_FIELD_WIDTH = 5000
PLAYING_FIELD_HEIGHT = 1000
# Size of the playing field.
MAIN_SCREEN_HEIGHT = SCREEN_HEIGHT
# How far away from the edges do we get before scrolling?
VIEWPORT_MARGIN = SCREEN_WIDTH / 2 - 50
TOP_VIEWPORT_MARGIN = 30
DEFAULT_BOTTOM_VIEWPORT = -10
# Control the physics of how the player moves
MAX_HORIZONTAL_MOVEMENT_SPEED = 10
MAX_VERTICAL_MOVEMENT_SPEED = 5
HORIZONTAL_ACCELERATION = 0.5
VERTICAL_ACCELERATION = 0.2
MOVEMENT_DRAG = 0.08
# How far the bullet travels before disappearing
BULLET_MAX_DISTANCE = SCREEN_WIDTH * 0.75
class Player(arcade.SpriteSolidColor):
""" Player ship """
def __init__(self):
""" Set up player """
super().__init__(40, 10, arcade.color.SLATE_GRAY)
self.face_right = True
def accelerate_up(self):
""" Accelerate player up """
self.change_y += VERTICAL_ACCELERATION
if self.change_y > MAX_VERTICAL_MOVEMENT_SPEED:
self.change_y = MAX_VERTICAL_MOVEMENT_SPEED
def accelerate_down(self):
""" Accelerate player down """
self.change_y -= VERTICAL_ACCELERATION
if self.change_y < -MAX_VERTICAL_MOVEMENT_SPEED:
self.change_y = -MAX_VERTICAL_MOVEMENT_SPEED
def accelerate_right(self):
""" Accelerate player right """
self.face_right = True
self.change_x += HORIZONTAL_ACCELERATION
if self.change_x > MAX_HORIZONTAL_MOVEMENT_SPEED:
self.change_x = MAX_HORIZONTAL_MOVEMENT_SPEED
def accelerate_left(self):
""" Accelerate player left """
self.face_right = False
self.change_x -= HORIZONTAL_ACCELERATION
if self.change_x < -MAX_HORIZONTAL_MOVEMENT_SPEED:
self.change_x = -MAX_HORIZONTAL_MOVEMENT_SPEED
def update(self):
""" Move the player """
# Move
self.center_x += self.change_x
self.center_y += self.change_y
# Drag
if self.change_x > 0:
self.change_x -= MOVEMENT_DRAG
if self.change_x < 0:
self.change_x += MOVEMENT_DRAG
if abs(self.change_x) < MOVEMENT_DRAG:
self.change_x = 0
if self.change_y > 0:
self.change_y -= MOVEMENT_DRAG
if self.change_y < 0:
self.change_y += MOVEMENT_DRAG
if abs(self.change_y) < MOVEMENT_DRAG:
self.change_y = 0
# Check bounds
if self.left < 0:
self.left = 0
elif self.right > PLAYING_FIELD_WIDTH - 1:
self.right = PLAYING_FIELD_WIDTH - 1
if self.bottom < 0:
self.bottom = 0
elif self.top > SCREEN_HEIGHT - 1:
self.top = SCREEN_HEIGHT - 1
class Bullet(arcade.SpriteSolidColor):
""" Bullet """
def __init__(self, width, height, color):
super().__init__(width, height, color)
self.distance = 0
def update(self):
""" Move the particle, and fade out """
# Move
self.center_x += self.change_x
self.center_y += self.change_y
self.distance += self.change_x
if self.distance > BULLET_MAX_DISTANCE:
self.remove_from_sprite_lists()
class Particle(arcade.SpriteSolidColor):
""" Particle from explosion """
def update(self):
""" Move the particle, and fade out """
# Move
self.center_x += self.change_x
self.center_y += self.change_y
# Fade
self.alpha -= 5
if self.alpha <= 0:
self.remove_from_sprite_lists()
class MyGame(arcade.Window):
""" Main application class. """
def __init__(self, width, height, title):
""" Initializer """
# Call the parent class initializer
super().__init__(width, height, title)
# Set the working directory (where we expect to find files) to the same
# directory this .py file is in. You can leave this out of your own
# code, but it is needed to easily run the examples using "python -m"
# as mentioned at the top of this program.
file_path = os.path.dirname(os.path.abspath(__file__))
os.chdir(file_path)
# Variables that will hold sprite lists
self.player_list = None
self.star_sprite_list = None
self.enemy_sprite_list = None
self.bullet_sprite_list = None
# Set up the player info
self.player_sprite = 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
self.view_bottom = 0
self.view_left = 0
# Set the background color
arcade.set_background_color(arcade.color.BLACK)
# --- Bloom related ---
# Frame to receive the glow, and color attachment to store each pixel's
# color data
self.bloom_color_attachment = self.ctx.texture((SCREEN_WIDTH, SCREEN_HEIGHT))
self.bloom_screen = self.ctx.framebuffer(
color_attachments=[self.bloom_color_attachment]
)
# Down-sampling helps improve the blur.
# Note: Any item with a size less than the down-sampling size may get missed in
# the blur process. Down-sampling by 8 and having an item of 4x4 size, the item
# will get missed 50% of the time in the x direction, and 50% of the time in the
# y direction for a total of being missed 75% of the time.
down_sampling = 4
# Size of the screen we are glowing onto
size = (SCREEN_WIDTH // down_sampling, SCREEN_HEIGHT // down_sampling)
# Gaussian blur parameters.
# To preview different values, see:
# https://observablehq.com/@jobleonard/gaussian-kernel-calculater
kernel_size = 21
sigma = 4
mu = 0
step = 1
# Control the intensity
multiplier = 2
# Create a post-processor to create a bloom
self.bloom_postprocessing = postprocessing.BloomEffect(size,
kernel_size,
sigma,
mu,
multiplier,
step)
def setup(self):
""" Set up the game and initialize the variables. """
# Sprite lists
self.player_list = arcade.SpriteList()
self.star_sprite_list = arcade.SpriteList()
self.enemy_sprite_list = arcade.SpriteList()
self.bullet_sprite_list = arcade.SpriteList()
# Set up the player
self.player_sprite = Player()
self.player_sprite.center_x = 50
self.player_sprite.center_y = 50
self.player_list.append(self.player_sprite)
# Add stars
for i in range(80):
sprite = arcade.SpriteSolidColor(4, 4, arcade.color.WHITE)
sprite.center_x = random.randrange(PLAYING_FIELD_WIDTH)
sprite.center_y = random.randrange(PLAYING_FIELD_HEIGHT)
self.star_sprite_list.append(sprite)
# Add enemies
for i in range(20):
sprite = arcade.SpriteSolidColor(20, 20, arcade.csscolor.LIGHT_SALMON)
sprite.center_x = random.randrange(PLAYING_FIELD_WIDTH)
sprite.center_y = random.randrange(PLAYING_FIELD_HEIGHT)
self.enemy_sprite_list.append(sprite)
def on_draw(self):
""" Render the screen. """
# This command has to happen before we start drawing
self.clear()
# --- Bloom related ---
# Draw to the 'bloom' layer
self.bloom_screen.use()
self.bloom_screen.clear((0, 0, 0, 0))
arcade.set_viewport(self.view_left,
SCREEN_WIDTH + self.view_left,
self.view_bottom,
SCREEN_HEIGHT + self.view_bottom)
# Draw all the sprites on the screen that should have a bloom
self.star_sprite_list.draw()
self.bullet_sprite_list.draw()
# Now draw to the actual screen
self.use()
arcade.set_viewport(self.view_left,
SCREEN_WIDTH + self.view_left,
self.view_bottom,
SCREEN_HEIGHT + self.view_bottom)
# --- Bloom related ---
# Draw the bloom layers
self.bloom_postprocessing.render(self.bloom_color_attachment, self)
# Draw the sprites / items that have no bloom
self.enemy_sprite_list.draw()
self.player_list.draw()
# Draw the ground
arcade.draw_line(0, 0, PLAYING_FIELD_WIDTH, 0, arcade.color.WHITE)
def on_update(self, delta_time):
""" Movement and game logic """
# Calculate speed based on the keys pressed
if self.up_pressed and not self.down_pressed:
self.player_sprite.accelerate_up()
elif self.down_pressed and not self.up_pressed:
self.player_sprite.accelerate_down()
if self.left_pressed and not self.right_pressed:
self.player_sprite.accelerate_left()
elif self.right_pressed and not self.left_pressed:
self.player_sprite.accelerate_right()
# Call update to move the sprite
self.player_list.update()
self.bullet_sprite_list.update()
for bullet in self.bullet_sprite_list:
enemy_hit_list = arcade.check_for_collision_with_list(bullet,
self.enemy_sprite_list)
for enemy in enemy_hit_list:
enemy.remove_from_sprite_lists()
for i in range(10):
particle = Particle(4, 4, arcade.color.RED)
while particle.change_y == 0 and particle.change_x == 0:
particle.change_y = random.randrange(-2, 3)
particle.change_x = random.randrange(-2, 3)
particle.center_x = enemy.center_x
particle.center_y = enemy.center_y
self.bullet_sprite_list.append(particle)
# Scroll left
left_boundary = self.view_left + VIEWPORT_MARGIN
if self.player_sprite.left < left_boundary:
self.view_left -= left_boundary - self.player_sprite.left
# Scroll right
right_boundary = self.view_left + SCREEN_WIDTH - VIEWPORT_MARGIN
if self.player_sprite.right > right_boundary:
self.view_left += self.player_sprite.right - right_boundary
# Scroll up
self.view_bottom = DEFAULT_BOTTOM_VIEWPORT
top_boundary = self.view_bottom + SCREEN_HEIGHT - TOP_VIEWPORT_MARGIN
if self.player_sprite.top > top_boundary:
self.view_bottom += self.player_sprite.top - top_boundary
self.view_left = int(self.view_left)
self.view_bottom = int(self.view_bottom)
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
elif key == arcade.key.SPACE:
# Shoot out a bullet/laser
bullet = arcade.SpriteSolidColor(35, 3, arcade.color.WHITE)
bullet.center_x = self.player_sprite.center_x
bullet.center_y = self.player_sprite.center_y
bullet.change_x = max(12, abs(self.player_sprite.change_x) + 10)
if not self.player_sprite.face_right:
bullet.change_x *= -1
self.bullet_sprite_list.append(bullet)
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 main():
""" Main function """
window = MyGame(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
window.setup()
arcade.run()
if __name__ == "__main__":
main()
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