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from visual import *
print """
Right button drag to rotate "camera" to view scene.
On a one-button mouse, right is Command + mouse.
Middle button to drag up or down to zoom in or out.
On a two-button mouse, middle is left + right.
On a one-button mouse, middle is Option + mouse.
"""
scene.title = "Lorenz differential equation"
scene.center = vector(25,0,0)
lorenz = curve( color = color.black, radius=0.3 )
# Draw grid
for x in arange(0,51,10):
box(pos=(x,0,0), axis=(0,0,50), height=0.4, width=0.4, color=(0.6,0.6,0.6) )
for z in arange(-25,26,10):
box(pos=(25,0,z), axis=(50,0,0), height=0.4, width=0., color=(0.6,0.6,0.6) )
dt = 0.01
y = vector(35, -10, -7)
for t in arange(0,10,dt):
# Integrate a funny differential equation
dydt = vector( - 8.0/3*y[0] + y[1]*y[2],
- 10*y[1] + 10*y[2],
- y[1]*y[0] + 28*y[1] - y[2] );
y = y + dydt*dt
# Draw lines colored by speed
c = clip( [mag(dydt) * 0.005], 0, 1 )[0]
lorenz.append( pos=y, color=(c,0, 1-c) )
rate( 500 )
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