by By: Jens in game development | pyglet | python

Last time i made a small demo using prerendered particle effects. Today i'll show another way of doing particle effects with python and pyglet. Instead of animating prerendered graphics i am going to use a particle system to create effects in realtime. The one i am using is py-lepton:

Lepton: A high-performance, pluggable particle engine and API for Python
Lepton is designed to make complex and beautiful particle effects possible, and even easy from Python programs.

Here is the demo of a simple explosion effect without using any premade texture. I made comments in the code that should explain everything.

The video:

Controls:

Left Mouse click : spawn new effect at center of the window

The Code: 

from lepton import Particle, ParticleGroup, default_system
from lepton.renderer import BillboardRenderer, PointRenderer
from lepton.texturizer import SpriteTexturizer, create_point_texture
from lepton.emitter import StaticEmitter
from lepton.controller import Gravity, Lifetime, Movement, Fader, ColorBlender, Growth

import pyglet
from pyglet.gl import *

#create pyglet window
window = pyglet.window.Window(visible=False)
window.clear()

#enable alpha blending
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA,GL_ONE)


def get_color(r,g,b,a):
    """ converts rgba values of 0 - 255 to the equivalent in 0 - 1"""
    return (r/255.0,g/255.0,b/255.0, a/255.0)

# Setting up particle group for all explosion particles with some controllers
# ColorBlending is from white to yellow to red/orange
# For visuals us a Pointtexture generated by py-lepton 
explosion = ParticleGroup(
    controllers=[
        Lifetime(4),
        Movement(damping=0.93),
        Growth(30),
        Fader( fade_in_start=0, start_alpha=0, fade_in_end=0.5 ,max_alpha=0.4, 
            fade_out_start=1, fade_out_end=4.0),
        ColorBlender([(0, get_color(255, 255, 255,255)), 
                      (0.75, get_color(255,255,0,255)), 
                      (1.5, get_color(255,0,0,255))
        ])
    ],
    renderer=PointRenderer(64, SpriteTexturizer(create_point_texture(64,5))))

# The explosion emitter, the thing actually creating the particles
# each particle starts at window center and add some variation (start position, size and
# life time)
explosion_emitter = StaticEmitter(
    template=Particle(
        position=(window.width/2,window.height/2,0), 
        size=(20,20,0),
        ), 
    deviation=Particle(
        position=(1,1,0), 
        size=(10,10,0),
        velocity=(100,100,0), 
        age=2
        ),
     )

#if left mouse button is clicked a new explosion will be started 
@window.event
def on_mouse_press(x, y, button, modifiers):
    if(pyglet.window.mouse.LEFT == button):
        explosion_emitter.emit(400, explosion)

# clear screen and draw particles
@window.event
def on_draw():
    window.clear()
    default_system.draw()

# setup scheduler for particle updates and start pyglet
if __name__ == '__main__':
    window.set_visible(True)
    pyglet.clock.schedule_interval(default_system.update, (1.0/30.0))
    pyglet.clock.set_fps_limit(None)
    pyglet.app.run()

Now spice up the explosion without using any premade texture and share it.

Happy hacking :-)

Update 1: Fixed get_color method