SuperCollider CLASSES (extension)

Brusselator
ExtensionExtension

Prigogine oscillator

//SLUGens released under the GNU GPL as extensions for SuperCollider 3, by Nick Collins, http://composerprogrammer.com/index.html 

Description

Euler ODE solver implementation of the Brusselator equations (http://en.wikipedia.org/wiki/Brusselator).

x' = x^2*y - (mu+1)*x + gamma

y' = -x^2*y + mu*x

All inputs can have .kr rate UGens plugged in.

Nonlinear oscillators can blow up, treat with caution. This one is relatively stable however, converging to a fixed point, or a limit cycle, in the upper positive quadrant. for some reasonable values. Just be careful if mu gets much bigger than gamma (though making it larger is necessary to get some chaotic oscillation behaviour); you can retrigger to get back to normal, and keep the rate lower to avoid Euler integration blow-ups. You may just need to scale and push down around zero to avoid a DC offset. Fixed point is at (x,y) = (gamma, mu/gamma)

Class Methods

*ar (reset: 0, rate: 0.01, mu: 1, gamma: 1, initx: 0.5, inity: 0.5, mul: 1, add: 0)

Arguments:

reset

If > 0.0, restart with new initial conditions sampled from initx, inity

rate

update rate for a sample step

mu

equation constant. Set mu > (gamma**2 + 1.0) for the more fun limit cycle regions

gamma

equation constant

initx

reset value for x

inity

reset value for y

Inherited class methods

Instance Methods

Inherited instance methods

Examples

//listen to x and y output
{Out.ar(0,Brusselator.ar(Impulse.kr(MouseY.kr(1,50,'exponential')),MouseX.kr(0.01,1,'exponential')))}.play

//avoid DC offset (default gamma is 1.0, listening to x only, so take off gamma
{Out.ar(0,Pan2.ar((Brusselator.ar(Impulse.kr(MouseY.kr(1,50,'exponential')),MouseX.kr(0.01,1,'exponential')))[0] - 1.0) )}.play


//fun time, stable oscillation with these parameters
{var mu = MouseY.kr(1.0,1.5); Out.ar(0,Pan2.ar(Brusselator.ar(0.0,MouseX.kr(0.01,0.1,'exponential'),mu,0.25)[0] ) )}.play


{ Out.ar(0,Pan2.ar(Brusselator.ar(Impulse.kr(10),MouseX.kr(0.01,0.1,'exponential'),1.5,0.25,MouseY.kr(-1.0,1.0),0.0)[0]) )}.play


{ Out.ar(0,Brusselator.ar(Impulse.kr(MouseY.kr(1,500,'exponential')),MouseX.kr(0.01,0.1,'exponential'),1.15,0.5,0.5,1.0) )}.play