Learning-Python/Particles/explosion.py
2020-06-30 14:43:37 +02:00

102 lines
2.7 KiB
Python

import random
import math
# the size of the screen
WIDTH = 800
HEIGHT = 600
# how much a particle slows down by each second
DRAG = 0.8
# the colour of each particle in R, G, B values
PARTICLE_COLOR = 255, 230, 128
# the time in seconds for which a particle is displayed
MAX_AGE = 3
# an array to hold the details of the explosion particles on the screen
particles = []
# This function creates a new explosion at the specified screen co-ordinates
def explode(x, y, speed=300):
# these are new particles, so set their age to zero
age = 0
# generate 100 particles per explosion
for _ in range(100):
# for each particle, generate a random angle and distance
angle = random.uniform (0, 2 * math.pi)
radius = random.uniform(0, 1) ** 0.5
# convert angle and distance from the explosion point into x and y velocity for the particle
vx = speed * radius * math.sin(angle)
vy = speed * radius * math.cos(angle)
# add the particle's position, velocity and age to the array
particles.append((x, y, vx, vy, age))
# This function redraws the screen by plotting each particle in the array
def draw():
# clear the screen
screen.clear()
# loop through all the particles in the array
for x, y, *_ in particles:
# for each particle in the array, plot its position on the screen
screen.surface.set_at((int(x), int(y)), PARTICLE_COLOR)
# This function updates the array of particles
def update(dt):
# to update the particle array, create a new empty array
new_particles = []
# loop through the existing particle array
for (x, y, vx, vy, age) in particles:
# if a particle was created more than a certain time ago, it can be removed
if age + dt > MAX_AGE:
continue
# update the particle's velocity - they slow down over time
drag = DRAG ** dt
vx *= drag
vy *= drag
# update the particle's position according to its velocity
x += vx * dt
y += vy * dt
# update the particle's age
age += dt
# add the particle's new position, velocity and age to the new array
new_particles.append((x, y, vx, vy, age))
# replace the current array with the new one
particles[:] = new_particles
# This function creates an explosion at a random location on the screen
def explode_random():
# select a random position on the screen
x = random.randrange(WIDTH)
y = random.randrange(HEIGHT)
# call the explosion function for that position
explode(x, y)
# call the random explosion function every 1.5 seconds
clock.schedule_interval(explode_random, 1.5)