@interface ViewController () 
@property (strong, nonatomic) CADisplayLink *displayLink;
@property (strong, nonatomic) CAShapeLayer *shapeLayer;
@property (strong, nonatomic) UIBezierPath *path;
@property (strong, nonatomic) CAShapeLayer *shapeLayer2;
@property (strong, nonatomic) UIBezierPath *path2;
@end

@implementation ViewController

- (void)viewDidLoad {
 [super viewDidLoad]; 

 _shapeLayer = [CAShapeLayer layer];
 _shapeLayer.frame = CGRectMake(0, 100, 375, 150);
 [self.view.layer addSublayer:_shapeLayer];
 

 _shapeLayer2 = [CAShapeLayer layer];
 _shapeLayer2.frame = CGRectMake(0, 100, 375, 150);
 [self.view.layer addSublayer:_shapeLayer2];


 _shapeLayer.fillColor = [[UIColor yellowColor] colorWithAlphaComponent:0.3].CGColor;
 _shapeLayer2.fillColor = [[UIColor blueColor] colorWithAlphaComponent:0.3].CGColor; 

 _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(drawPath)];
 [_displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes]; 

} 

- (void)drawPath {

 static double i = 0;
 
 CGFloat A = 10.f;//A振幅
 CGFloat k = 0;//y軸偏移
 CGFloat ω = 0.03;//角速度ω變大，則波形在X軸上收縮（波形變緊密）；角速度ω變小，則波形在X軸上延展（波形變稀疏）。不等于0
 CGFloat φ = 0 + i;//初相，x=0時的相位；反映在坐標系上則為圖像的左右移動。

 //y=Asin(ωx+φ)+k 

 _path = [UIBezierPath bezierPath];
 _path2 = [UIBezierPath bezierPath]; 

 [_path moveToPoint:CGPointZero];
 [_path2 moveToPoint:CGPointZero];
 for (int i = 0; i < 376; i ++) {

  CGFloat x = i;

  CGFloat y = A * sin(ω*x+φ)+k;
  CGFloat y2 = A * cos(ω*x+φ)+k;
  [_path addLineToPoint:CGPointMake(x, y)];
  [_path2 addLineToPoint:CGPointMake(x, y2)];

 }
 [_path addLineToPoint:CGPointMake(375, -100)];
 [_path addLineToPoint:CGPointMake(0, -100)];
 _path.lineWidth = 1;
 _shapeLayer.path = _path.CGPath; 

 [_path2 addLineToPoint:CGPointMake(375, -100)];
 [_path2 addLineToPoint:CGPointMake(0, -100)];
 _path2.lineWidth = 1;

  _shapeLayer2.path = _path2.CGPath;

 

 i += 0.1;

 if (i > M_PI * 2) {

  i = 0;//防止i越界

 }

}