from visual import *

scene.autoscale=0
scene.range=40.0

## don't display the ball - boring
#scene.visible=0

def force(pos,t):
    result = vector(0,0,0)
    sigma=10.0
    b=8.0/3.0
    r=25.0
    result.x=sigma*(pos.y-pos.x)
    result.y=-pos.x*pos.z+r*pos.x-pos.y
    result.z=pos.x*pos.y-b*pos.z
    return result
    
    
ball=sphere(pos=vector(1.0,0.0,0),color=color.red,
            track=curve(radius=0.1,color=color.green))

dt=0.0001
t=0

while (1) :
#    rate(1000)
    t=t+dt
# euler alg.
    ball.pos=ball.pos+force(ball.pos,t)*dt
    ball.track.append(pos=ball.pos)