Arrow-splosion .. simple particle system in shoebot.

arrow_particles.bot.py

#
# (Very) Simple particle system implementation in shoebot
#
# to run, install shoebot and planar.py, then run
#
# sbot -w arrow_particles.bot

from random import random

from planar.py import Vec2, Affine
from collections import namedtuple


class Moveable(object):
    """
    Moveable object.

    Controller functions manage the movement and are called on 'update'
    """
    def __init__(self, pos = None, velocity = None, angle = None, controller = None, controllers = None, draw_func = None):
        self.pos = pos or Vec2(WIDTH / 2, HEIGHT / 2)
        self.velocity = velocity or 0.0
        self.angle = angle or 0
        self.draw_func = draw_func
        if controller:
            self.controllers = [ controller ]
        else:
            self.controllers = []
        if controllers:
            self.controllers.extend(controllers)

    def update(self):
        """
        Call all the controllers to update coordinates.
        
        Angles are always wrapped to 360 degrees.
        """
        pos, angle, velocity = self.pos, self.angle, self.velocity
        for controller in self.controllers:
            pos, angle, velocity = controller(pos, angle % 360, velocity)
        self.pos, self.angle, self.velocity = pos, angle % 360, velocity
        self.pos += Vec2.polar(angle = angle, length = velocity)

    def draw(self):
        push()
        translate(self.pos.x, self.pos.y)
        rotate(-self.angle) # nodebox1/shoebot rotation is anticlockwise
        self.draw_func()
        pop()



class Particle(Moveable):
    def __init__(self, hp = 250, **kwargs):
        Moveable.__init__(self, draw_func = self.draw_func, **kwargs)
        self.hp = hp

    def update(self):
        super(Particle, self).update()
        self.hp -=1
        return self.hp > 0

    def draw_func(self):
        a = 1.0
        if 0 < self.hp < 250:
           a = self.hp / 250.0
        arrow(0, 0, 80, fill=(1, 0, 0, a))



#def key_controller(pos, angle, velocity):
#    if keydown:
#        if keycode == KEY_UP:
#            velocity += 0.2
#        elif keycode == KEY_DOWN:
#            velocity -= 0.2
#        elif keycode == KEY_LEFT:
#            angle -= 5
#        elif keycode == KEY_RIGHT:
#            angle += 5
#        elif keycode == KEY_SPACE:
#            velocity *= 0.9
#        elif keycode == KEY_RETURN:
#            pos = Vec2(WIDTH / 2, HEIGHT / 2)
#            velocity = 0.0
#            angle = 0
#    return pos, angle, velocity


def inertia_controller(pos, angle, velocity):
    return pos, angle, velocity * 0.99


def bounds_controller(pos, angle, velocity):
    if pos.x < 10 or pos.x > WIDTH:
        angle = 180 - angle
    if pos.y < 10 or pos.y > HEIGHT - 10:
        angle = - angle
    return pos, angle, velocity



def random_emitter(particles):
    if random() > 0.1:
        p = Particle(
            velocity = random() * 2.0,
            angle = random() * 360,
            controller = inertia_controller)
        particles.append(p)


def update_particles(particles):
    '''
    Update particles
    
    return: list of particles to update
    '''
    part = []
    for p in particles:
        if p.update():
            part.append(p)
    return part



def setup():
    global particles
    speed(60)
    size(800, 600)
    transform(mode=CENTER)

    particles = []
    

def draw():
    global particles

    random_emitter(particles)
    particles = update_particles(particles)

    for p in particles:
        p.draw()