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Audiovisuals with SC - Example14 - particle system

See /f0blog/audiovisuals-with-sc/

//Example14 - particle system
//click and drag in the window
(
s.latency= 0.05;
s.waitForBoot{
    //--window setup
    var width= 640, height= 480;
    var w= Window("Example14 - particle system", Rect(99, 99, width, height), false);
    var u= UserView(w, Rect(0, 0, width, height));
    //--variables
    var synths= ();  //keep track of synths objects
    var prev= Point(0, 0);  //previous mouse position
    var mouse= prev;
    var parts= [];
    var makePart= {|pnt|  //pseudo class
        (
            \vel: Point(2.0.rand2, 10.rand.neg),  //velocity vector
            \pos: pnt,
            \age: (~dead*0.5).linrand,
            \mas: ~mass.rand,
            \syn: Synth(\av)
        )
    };
    SynthDef(\av, {|freq= 400, fm= 1, beat= 1, amp= 0, pan= 0, gate= 1|
        var e= EnvGen.ar(Env.asr(0.01, 1, 0.02), gate, doneAction:2);
        var z= SinOsc.ar(freq*SinOsc.ar(0, SinOsc.ar(fm, 0, 2pi), beat), 0, amp);
        Out.ar(0, Pan2.ar(z, pan, e));
    }, #[0.05, 0.05, 0.05, 0.05, 0.05]).add;
    s.sync;
    u.mouseMoveAction_{|v, x, y| mouse= Point(x, y)};  //update mouse position
    //--interface
    ~dead= 500;  //max age
    ~mass= 1.5;  //max mass
    ~damp= 0.98;  //general damping
    ~grav= Point(0, 0.98);  //gravity vector
    //--main loop
    u.drawFunc= {
        if(mouse!=prev, {
            prev= mouse;
            parts= parts.add(makePart.value(prev));  //new particle
        });
        parts= parts.select{|p|  //remove old ones
            if(p.age<~dead, {
                true;
            }, {
                p.syn.release;
                false;
            });
        };
        parts.do{|p|  //update each ball
            var r;
            p.vel= p.vel+(~grav*p.mas);  //apply gravity force
            p.vel= p.vel*~damp;  //general damping
            if(p.pos.x>width or:{p.pos.x<0}, {  //bounce leftright bounds
                p.vel= p.vel*Point(-1, 1);
            });
            if(p.pos.y>height or:{p.pos.y<0}, {  //bounce topbottom bounds
                p.vel= p.vel*Point(1, -1);
            });
            p.pos= p.pos+p.vel;  //move the ball
            p.age= p.age+1;
            p.syn.set(  //system maps to sound
                \freq, p.pos.y.linexp(0, height, 2000, 200),
                \amp, p.pos.y.linlin(0, height, p.mas, 0)*(1-(p.age/~dead))*0.1,
                \fm, p.mas*p.pos.x,
                \beat, p.vel.asComplex.magnitude,  //ball velocity mapped to beat
                \pan, p.pos.x.linlin(0, width, -1, 1)
            );
            r= 1-(p.age/~dead)*p.mas*10;  //radius
            Pen.fillColor= Color.grey(1-(p.age/~dead), 1);
            Pen.fillOval(Rect.aboutPoint(p.pos, r, r));
        };
    };
    //--window management
    u.clearOnRefresh= true;
    u.background= Color.black;
    w.onClose= {parts.do{|p| p.syn.free}};
    w.front;
    u.animate= true;
    CmdPeriod.doOnce({if(w.isClosed.not, {w.close})});
};
)
//change these while the program is running
~mass= 4;
~grav= Point(0.1, 0.1);
~grav= Point(-0.1, -0.1);
~damp= 0.9;
//close the window to stop or press cmd+.