Gravitational drawing

Quick&dirty sketch using the Newton's law of universal gravitation in Nodebox.
http://en.wikipedia.org/wiki/Gravitational_force

Hit 'p'/'o' to show or hide the trailing path.

The 'earth' is not affected by the gravity since it has a rigid link to mousex and mousey.

ciaociao
G.

from math import *
 
size(600, 600)
speed(60)
 
def setup():
    global moon1, moon2, earth, path1, path2, d
    moon1 = Planet(x=random(0, WIDTH), y=random(0, HEIGHT), mass=20.0)
    earth = MousePlanet(mass=30.0)
    path1 = []  
    d = True  
 
def draw():
	
    background(0.4,0.2,0)
    global d
 
    # to do: check if the mouse goes off-stsage etc etc..
    g1 = gravity(earth, moon1, k=20.5)
    
    earth.update()
    moon1.update(g1)
     
    nofill()
    strokewidth(2)
    autoclosepath(False)  
    stroke(1, 0.75)
 
    pt1 = Point(moon1.x, moon1.y)
    path1.append(pt1)
 
    if key == 'p':
        d = False # don't show the path
    if key == 'o':
        d = True # show the path
    
    if d == True:
        if len(path1) > 0:
            first = True
            for pt in path1:
                if first:
                    beginpath(pt.x, pt.y)
                    first = False
                else:
                    lineto(pt.x, pt.y)
            endpath()
 
    earth.draw()
    moon1.draw()
 
 
class Planet:
        
	def __init__(self, x, y, mass=1.0):
	   self.x = x
	   self.y = y
	   self.mass = mass
	   self.s = self.mass*1 # size
	   self.r = self.s*0.5 # radius
	   self.alive = True # not used yet
	   self.v_x = 0
	   self.v_y = 0
	
	def draw(self):
	    fill(1, 0.8)
	    nostroke()
	    oval(self.x-self.r, self.y-self.r, self.s, self.s)
	
	def update(self, g):
	    a_x = g[0] / self.mass
	    a_y = g[1] / self.mass
	    self.v_x += a_x
	    self.v_y += a_y
	    self.x += self.v_x
	    self.y += self.v_y	    
 
 
class MousePlanet:
        
	def __init__(self, mass=1.0):
	   self.x = MOUSEX
	   self.y = MOUSEY
	   self.mass = mass
	   self.s = self.mass*2
	   self.r = self.s*0.5
	   self.alive = True
	
	def draw(self):
	    fill(0.5, 0.9, 1, 0.5)
	    nostroke()
	    oval(self.x-self.r, self.y-self.r, self.s, self.s)
	
	def update(self):
	    self.x = MOUSEX
	    self.y = MOUSEY
 
 
def gravity(obj1, obj2, k=0.5):
    dist = distance(obj1.x, obj1.y, obj2.x, obj2.y)
    limit = max(obj1.s, obj2.s)
    if dist < limit:
        dist = limit    
    grav = ( (obj1.mass * obj2.mass) / (dist * dist) ) * k 
    grav_x = grav * ( (obj1.x - obj2.x) / dist )
    grav_y = grav * ( (obj1.y - obj2.y) / dist )
    return (grav_x, grav_y)
   
def distance(x0, y0, x1, y1):
    return sqrt((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0))

Very nice work, Giorgio, as usual. You certainly know how to move the earth! (btw I keep on getting very good comments about your presentation at integrated2009 especially from the fine arts department, you opened their eyes (minds?)...)

thanks lucas.
after some ping-pong coding in the studio, here's an updated version of the above sketch.

user manual:
— hit '+' to add a satellite
— hit 'p' to hide or show the satellites

PS
HOW DO I POST AN IMAGE IN A COMMENT?

from math import *
 
size(630, 780)
speed(60)
 
def setup():
    global earth, d, moons, keypressed
    earth = MousePlanet(mass=30.0)
    moons = []
    d = True
    keypressed = '' 
 
def draw():
    
    background(0.4,0.2,0)
    global d,keypressed
 
    # to do: check se il mouse va offstsage
    
    earth.update()
    for m in moons:
        g = gravity(earth, m, k=200)
        m.update(g)
     
    nofill()
    strokewidth(2)
    autoclosepath(False)  
    
    if keydown:
        keypressed = key
        
    if not keydown and keypressed:    
        if key == 'p':
            d = not d
        elif key == '+':
            moons.append(Planet(x=random(0, WIDTH), y=random(0, HEIGHT), mass=random(5,25)))
        keypressed = ''
    
    if d:
        for m in moons:
            m.showpath()
 
    earth.draw()
    for m in moons:
        m.draw()
 
 
class Planet:
        
    def __init__(self, x, y, mass=1.0):
       self.x = x
       self.y = y
       self.mass = mass
       self.s = self.mass*1 # size
       self.r = self.s*0.5 # radius
       self.alive = True
       self.v_x = 0
       self.v_y = 0
       self.path = []
    
    def draw(self):
        self.path.append(Point(self.x, self.y))
        fill(1, 0.8)
        nostroke()
        oval(self.x-self.r, self.y-self.r, self.s, self.s)
        
    def showpath(self):
        if len(self.path) > 0:
            stroke(1, 0.75)
            first = True
            for pt in self.path[-20:]:
                if first:
                    beginpath(pt.x, pt.y)
                    first = False
                else:
                    lineto(pt.x, pt.y)
            endpath()
        
    
    def update(self, g):
        a_x = g[0] / self.mass # acceleration
        a_y = g[1] / self.mass
        self.v_x += a_x
        self.v_y += a_y
        self.x += self.v_x
        self.y += self.v_y        
 
 
class MousePlanet:
        
    def __init__(self, mass=1.0):
       self.x = MOUSEX
       self.y = MOUSEY
       self.mass = mass
       self.s = self.mass*2
       self.r = self.s*0.5
       self.alive = True
    
    def draw(self):
        fill(0.5, 0.9, 1, 0.5)
        nostroke()
        oval(self.x-self.r, self.y-self.r, self.s, self.s)
    
    def update(self):
        self.x = MOUSEX
        self.y = MOUSEY
 
 
def gravity(obj1, obj2, k=0.5):
    dist = distance(obj1.x, obj1.y, obj2.x, obj2.y)
    limit = max(obj1.s, obj2.s)
    if dist < limit:
        dist = limit    
    grav = ( (obj1.mass * obj2.mass) / (dist * dist) ) * k 
    grav_x = grav * ( (obj1.x - obj2.x) / dist )
    grav_y = grav * ( (obj1.y - obj2.y) / dist )
    return (grav_x, grav_y)
   
def distance(x0, y0, x1, y1):
    return sqrt((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0))

This idea has been on my to-do list for a little while now! Thanks a lot for sharing, Giorgio! I don't think I'll get around to playing with this for a couple of weeks, but I'll post if I come up with anything interesting.

There is definitely so many things that you an do with this. The options are endless with this. The code is definitely so good. Toronto Mortgage