curves.m

//
//  ViewController.m
//  Path
//
//  Created by Julius Parishy on 7/28/18.
//  Copyright © 2018 JP. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIView *containerView;

@property (nonatomic, assign) CGFloat angleOffset;
@property (nonatomic, weak) CAShapeLayer *shapeLayer;

@property (nonatomic, strong) CADisplayLink *displayLink;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    [self setupCurveLayer];
    
    self.angleOffset = 0;
    
    self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(updatePath)];
    [self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}

- (void)viewDidLayoutSubviews
{
    [super viewDidLayoutSubviews];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)setupCurveLayer
{
    if (self.shapeLayer)
    {
        [self.shapeLayer removeFromSuperlayer];
    }
    
    CAShapeLayer *layer = [CAShapeLayer layer];
    layer.fillColor = [[UIColor purpleColor] CGColor];
    
    [self.containerView.layer addSublayer:layer];
    
    self.shapeLayer = layer;
}

- (void)updatePath
{
    self.angleOffset += (M_PI / 2.0 / 20.0);
    
    CGFloat width = CGRectGetWidth(self.containerView.bounds);
    
    CGFloat midY = CGRectGetMidY(self.containerView.bounds);
    
    UIBezierPath *path = [UIBezierPath bezierPath];
    [path moveToPoint:CGPointMake(0, midY)];
    
    NSInteger steps = 300;
    NSInteger numCurves = 5;
    CGFloat amplitude = midY;
    for (NSInteger i = 0; i < steps; ++i)
    {
        CGFloat stepAngle = (M_PI / (steps / numCurves)) * i;
        CGFloat delta = sinf(self.angleOffset + stepAngle);
        
        CGPoint point = CGPointZero;
        point.x = (width / steps) * i;
        point.y = midY + (delta * amplitude);
        
        [path addLineToPoint:point];
    }
    
    [path addLineToPoint:CGPointMake(width, midY)];
    
    self.shapeLayer.frame = self.containerView.bounds;
    self.shapeLayer.path = [path CGPath];
}

@end