#!/usr/bin/env python
"""A simple example demonstrating the creation of actors and animating
the in a scene using visual modeule."""
# Author: Raashid Baig <raashid@aero.iitb.ac.in>
# License: BSD Style.

from enthought.tvtk.tools.visual import *
from math import sqrt

#Creating the actors for the scene
giant = sphere( pos = (-1.0e11, 0, 0), radius = 2e10, color = (1, 0, 0), mass = 2e30)
dwarf = sphere( pos = (1.5e11, 0, 0), radius = 1e10, color = (1, 1, 0), mass = 1e30)
giant.p = vector(0, 0, -1e4)*giant.mass
dwarf.p = -1*giant.p    
# creating the curve which will trace the paths of actors
for a in [giant, dwarf]:
    a.orbit = curve(radius = 2e9, color = a.color)
    
dt = 86400

def anim():
    #Creating the animation function which will be called at
    #uniform timeperiod through the iterate function
    dist = dwarf.pos - giant.pos
    force = 6.7e-11 * giant.mass * dwarf.mass * dist/(sqrt(dist[0]**2 + dist[1]**2 + dist[2]**2))**3
    giant.p = giant.p + force*dt
    dwarf.p = dwarf.p - force*dt

    for a in [giant, dwarf]:
        a.pos = a.pos + (a.p/a.mass)*dt
        a.orbit.append(a.pos)
        p = a.orbit.points
        if len(p) > 1000:
            a.orbit.points = p[200:]

a = iterate(50, anim)
a.edit_traits()
show()