ios - SpriteKit 生成随机 curl 线

Question

我正在做一个项目，我需要完成的是生成随机 curl 线。此时我已经有了一条随机生成的线，但它不是 curl 的。我每 0.5 秒在不同的 x 位置生成点，并将这些点与贝塞尔曲线连接起来。一切都完美无缺，只是它不是 curl 的。下图显示了 1) 我现在如何拥有它以及 2) 我想如何制作它。我该怎么做？我正在使用 SpriteKit - Objective C

Answer 1

基本上，您需要制作和随机化 A Bézier(参数)曲线的条件是 control points .

在你阅读了那个很好的答案并熟悉术语后，你可以试试这个例子(我假设你的场景和 View 大小设置正确):

GameScene.m

#import "GameScene.h"

@implementation GameScene

-(void)didMoveToView:(SKView *)view {

}

-(NSInteger)randomNumberBetween:(NSInteger)from to:(NSInteger)to {

    return (int)from + arc4random() % (to-from+1);
}


- (CGMutablePathRef)generatePath
{
    CGMutablePathRef path = CGPathCreateMutable();

    CGPoint p0 =  CGPointMake(CGRectGetMidX(self.frame),self.scene.size.height-20.0f); //starting point just little below the upper edge of the screen

    CGPathMoveToPoint(path, nil, p0.x, p0.y);

    CGPoint p1 =
    CGPointMake([self randomNumberBetween:150 to:300], self.scene.size.height- [self randomNumberBetween:150 to:300]);

     CGPoint p2 = CGPointMake([self randomNumberBetween:150 to:300],[self randomNumberBetween:150 to:300]);

    CGPoint p3 = CGPointMake(CGRectGetMidX(self.frame),0 + 20.0f); //ending point, just little above the bottom edge of the screen

    CGFloat v = 0.3;

    CGFloat cp1x = p1.x+v * (p1.x-p0.x);
    CGFloat cp1y = p1.y+v *  (p1.y-p0.y);
    CGFloat cp2x = p2.x-v *  (p3.x-p2.x);
    CGFloat cp2y = p2.y-v *  (p3.y-p2.y);




    CGPathAddCurveToPoint(path,nil,cp1x,cp1y,cp2x,cp2y,p3.x,p3.y);



    /*Debug - not needed*/


    SKSpriteNode *sp0 = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(5.0f,5.0f)];
    sp0.zPosition = 5;
    sp0.position = p0;
    SKLabelNode *lp0 = [SKLabelNode labelNodeWithFontNamed:@"ArialMT"];
    lp0.fontColor = [SKColor whiteColor];
    lp0.fontSize = 20.0f;
    lp0.text = @"p0";
    lp0.position = CGPointMake(0.0f,-20.0f);
    [sp0 addChild:lp0];
    [self addChild:sp0];


    SKSpriteNode *sp1 = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(5.0f,5.0f)];
    sp1.zPosition = 5;
    sp1.position = p1;
    SKLabelNode *lp1 = [SKLabelNode labelNodeWithFontNamed:@"ArialMT"];
    lp1.fontColor = [SKColor whiteColor];
    lp1.fontSize = 20.0f;
    lp1.position = CGPointMake(0.0f,15.0f);
    lp1.text = @"p1";
    [sp1 addChild:lp1];
    [self addChild:sp1];

    SKSpriteNode *sp2 = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(5.0f,5.0f)];
    sp2.zPosition = 5;
    sp2.position = p2;
    SKLabelNode *lp2 = [SKLabelNode labelNodeWithFontNamed:@"ArialMT"];
    lp2.fontColor = [SKColor whiteColor];
    lp2.fontSize = 20.0f;
    lp2.position = CGPointMake(0.0f,15.0f);
    lp2.text = @"p2";
    [sp2 addChild:lp2];
    [self addChild:sp2];


    SKSpriteNode *sp3 = [SKSpriteNode spriteNodeWithColor:[SKColor yellowColor] size:CGSizeMake(5.0f,5.0f)];
    sp3.zPosition = 5;
    sp3.position = p3;
    SKLabelNode *lp3 = [SKLabelNode labelNodeWithFontNamed:@"ArialMT"];
    lp3.fontColor = [SKColor whiteColor];
    lp3.fontSize = 20.0f;
    lp3.position = CGPointMake(0.0f,15.0f);
    lp3.text = @"p3";
    [sp3 addChild:lp3];
    [self addChild:sp3];



    SKShapeNode *p0p1 = [SKShapeNode node];
    p0p1.zPosition = 2;
    CGMutablePathRef path1 = CGPathCreateMutable();
    CGPathMoveToPoint(path1, NULL, p0.x, p0.y);
    CGPathAddLineToPoint(path1, NULL, p1.x, p1.y);
    p0p1.path = path1;
    [p0p1 setStrokeColor:[UIColor greenColor]];
    [self addChild:p0p1];

    SKShapeNode *p2p3 = [SKShapeNode node];
    p2p3.zPosition = 2;
    CGMutablePathRef path2 = CGPathCreateMutable();
    CGPathMoveToPoint(path2, NULL, p2.x, p2.y);
    CGPathAddLineToPoint(path2, NULL, p3.x, p3.y);
    p2p3.path = path2;
    [p2p3 setStrokeColor:[UIColor greenColor]];
    [self addChild:p2p3];

    return path;
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

    [self removeAllChildren];

    SKShapeNode *yourline = [SKShapeNode node];
    yourline.zPosition = 1;

    yourline.path = [self generatePath];

    [yourline setLineWidth:5];

    [yourline setStrokeColor:[SKColor redColor]];

    [self addChild:yourline];

}

此代码的大部分用于可视化调试，不需要它来随机化曲线。重要的部分是方法 generatePath 的第一部分。这是结果: