ios - 使用 SKPhysics(碰撞)拖动 SKSpriteNode(跟随你的手指移动)

Question

想要使用 SKPhysics(启用碰撞)拖动 SKSpriteNode(跟随您的手指移动)

2 失败的解决方案:

1)

a) 解决方案:改变SKSpriteNode的位置

b) 问题:当用户拖动 spriteNode 快速穿过墙壁时，SKSpriteNode 会“神奇地”穿过墙壁(Physics 似乎不起作用)

c)代码:

@property (nonatomic) CGPoint translationBy;

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    [self selectNodeForTouch:positionInScene];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPoint previousPosition = [touch previousLocationInNode:self];

    CGPoint translation = CGPointMake(positionInScene.x - previousPosition.x, positionInScene.y - previousPosition.y);

    [self panForTranslation:translation];
}

- (void)panForTranslation:(CGPoint)translation {
    CGPoint position = [_selectedNode position];
    if([[_selectedNode name] isEqualToString:PLAYER_NAME]) {
        [_selectedNode setPosition:CGPointMake(position.x + translation.x, position.y + translation.y)];
    }
}

2) 在这里搜索后找到了这个 advice by @LearnCocos2D “当你使用物理时，坚持通过力、脉冲或直接改变 body 速度来移动物理 body 。”所以我尝试了:

a) 解决方案:在 Sprite 节点上施加脉冲。

b) 问题:即使我没有拖动 Sprite 节点， Sprite 节点也会继续移动。 (表现得像一艘漂浮的船。期望它表现得像一辆汽车，一旦拖动停止， Sprite 节点将停止；一旦拖动开始，它将跟随手指。)

c) 代码:

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    [self selectNodeForTouch:positionInScene];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPoint previousPosition = [touch previousLocationInNode:self];

    CGPoint translation = CGPointMake(positionInScene.x - previousPosition.x, positionInScene.y - previousPosition.y);

    CGVector forceVector = CGVectorMake(translation.x, translation.y);
    [self.player.physicsBody applyImpulse:forceVector];
    //[self.player.physicsBody setVelocity:CGVectorMake(0, 0)];

}

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更新:

来自评论:“i)您可以确定节点到手指位置的距离，然后在每次更新时设置速度:以便下一帧它准确地位于手指的位置。ii)如果手指和节点位置相同，这将取消避免任何移动，否则节点会在执行所有物理碰撞时粘在你的手指上，并在手指被阻挡的情况下继续插入自身和手指之间的物体。”

a) 问题:如何禁用轻弹？

b) 问题: Sprite 节点会因轻微(意外)轻弹而移动到很远的地方。

c)代码:

@property (nonatomic) CGPoint translationBy;

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint positionInScene = [touch locationInNode:self];
    CGPoint previousPosition = [touch previousLocationInNode:self];
    //    1) You could determine the distance of the node to the finger location,

    CGPoint xyTranslation = CGPointMake(positionInScene.x - previousPosition.x, positionInScene.y - previousPosition.y);
    if (fabsf(positionInScene.x - previousPosition.x) < kPlayerMovementThreshold) {
        xyTranslation.x  = 0;
    }
    if (fabsf(positionInScene.y - previousPosition.y) < kPlayerMovementThreshold) {
        xyTranslation.y = 0;
    }
    self.translationBy = xyTranslation;
}

static const CGFloat kPlayerMovementSpeed = 55.0f;

static const CGFloat kPlayerMovementThreshold = 1.0f;

-(void)update:(CFTimeInterval)currentTime{
     // ii) then set the velocity every update: so that it will exactly be on the finger's position the next frame.

    CGFloat dx = self.translationBy.x*kPlayerMovementSpeed;
    CGFloat dy = self.translationBy.y*kPlayerMovementSpeed;
    CGVector velocityVector = CGVectorMake(dx,dy);
    [self.player.physicsBody setVelocity:velocityVector];
}

Answer 1

我所做的是制作一个 SKNode，我们称它为“a”，并附有一个非常小的物理体。这个新节点通过 SKPhysicsJointSpring 连接到我要移动的节点，我们称之为“b”。新节点 a 跟踪我的手指移动， Spring 确保目标节点 b 跟随它。因为节点 b 使用物理定位，所以碰撞检测按预期工作。