some stuff for working with simplex noise in dart

noise.dart

class VisualizerPainter extends CustomPainter {
  final double position;
  var noise = new SimplexNoise();
  NoiseLoop rLoop;
  NoiseLoop gLoop;
  NoiseLoop bLoop;

  VisualizerPainter(this.position, this.rLoop, this.gLoop, this.bLoop);

  @override
  void paint(Canvas canvas, Size size) {
    print(rLoop.value(position));
    Offset center = Offset(size.width / 2, size.height / 2);
    var radius = min(size.width, size.height);

    Path path = Path();
    path.moveTo(center.dx + radius * rLoop.value(position), center.dy);
    for (int i = 0; i != 100; i++) {
      var angle = map(0.0 + i, 0, 100, 0, 2 * pi);
      path.lineTo(center.dx + cos(angle) * radius * rLoop.value(position),
          center.dy + sin(angle) * radius * rLoop.value(position));
    }
    canvas.drawPath(path, Paint()..color = Colors.black);

//    canvas.drawRect(
//        Rect.fromLTWH(0, 0, size.width, size.height), Paint()..color = color);
  }

  @override
  bool shouldRepaint(VisualizerPainter oldDelegate) =>
      position != oldDelegate.position;
}

double map(
    double value, double istart, double istop, double ostart, double ostop) {
  return ostart + (ostop - ostart) * ((value - istart) / (istop - istart));
}

class NoiseLoop {
  var noise = new SimplexNoise();
  final double radius;
  var x;
  var y;

  NoiseLoop(this.radius) {
    x = new Random().nextInt(100) + radius;
    y = new Random().nextInt(100) + radius;
  }

  double value(double a) => map(
      noise.getSimplex2(cos(map(a, 0, 1, 0, 2 * pi)) * radius + x,
          sin(map(a, 0, 1, 0, 2 * pi)) * radius + y),
      -0.8,
      0.8,
      0,
      1);
}