SpriteKit 中的简单销接头无法按预期工作答案

【问题标题】：Simple pin joint in SpriteKit doesn't work as expectedSpriteKit 中的简单销接头无法按预期工作
【发布时间】：2017-07-24 02:07:51
【问题描述】：

我想做一个钟摆。从 SKScene 开始，一切都默认，我执行以下操作...

- (void)createSceneContents {
    self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.view.bounds];

    // object 1 is the fulcrum
    SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
    [self addChild:object1];
    object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
    object1.physicsBody.dynamic = NO;
    object1.position = self.view.center;

    // object2 is like a broomstick, which I will pin to the fulcrum
    SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
    [self addChild:object2];
    object2.anchorPoint = CGPointMake(0.0, 0.5);
    object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];
    object2.position = self.view.center;

    // pin the physics bodies
    SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:object1.position];
    [self.physicsWorld addJoint:pinJoint];
}

如果我不添加 pin 逻辑，支点会像预期的那样停留在场景的中间，并且扫帚柄会掉到地板上，所以我知道扫帚柄会受到重力的影响。添加引脚后，我得到了这个：

没有动作。为什么？这也不会导致任何运动......

[object2.physicsBody applyForce:CGVectorMake(0, -5)];

我预计扫帚柄会摆动和摆动，因为它固定在支点上。我已经看过关于在关节之前先定位节点的文章，但我已经做到了。我期望扫帚摆动我错了吗？我怎样才能让它这样做？

【问题讨论】：

标签： ios objective-c sprite-kit skphysicsjoint

【解决方案1】：

节点 2 有错误定义的锚点，这里上传一个示例：

Full code of example

图片：

Swift 3 代码：

    let nodeSize = CGSize(width: 10, height: 10)
    let node = SKSpriteNode(color: .red, size: nodeSize)
    node.physicsBody = SKPhysicsBody(rectangleOf: nodeSize)
    node.physicsBody?.isDynamic = false
    self.addChild(node)

    let node2Size = CGSize(width: 60, height: 8)
    let node2 = SKSpriteNode(color: .green, size: node2Size)
    node2.position = CGPoint(x: 30, y: 0)
    node2.physicsBody = SKPhysicsBody(rectangleOf: node2Size)
    node2.physicsBody?.mass = 1.0
    self.addChild(node2)


    let a = SKPhysicsJointPin.joint(withBodyA: node.physicsBody! , bodyB: node2.physicsBody!, anchor: CGPoint(x: 0.0, y: 0.0))
    self.physicsWorld.add(a)

目标-C：

SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
[self addChild:object1];
object1.position = self.view.center;
object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
object1.physicsBody.dynamic = NO;

SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
[self addChild:object2];
object2.position = CGPointMake(self.view.center.x+45, self.view.center.y);

object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];

SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:self.view.center];
[self.physicsWorld addJoint:pinJoint];

【讨论】：

非常感谢。我发布了目标 C 翻译。（不确定如何在不定位节点的情况下使其工作）。
默认情况下，节点设置在 0,0，node2 设置在另一个位置 :)
再次感谢您。它让我遇到了一个新问题，我在这里询问stackoverflow.com/questions/45259118/… 肯定会感谢任何想法。

【解决方案2】：

感谢@Maetschl，我能够使其在 Objective-c 中按如下方式工作（移除锚点并将摆动节点定位到一个边缘）...

SKSpriteNode *object1 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:CGSizeMake(5, 5)];
[self addChild:object1];
object1.position = self.view.center;
object1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object1.frame.size];
object1.physicsBody.dynamic = NO;

SKSpriteNode *object2 = [SKSpriteNode spriteNodeWithColor:[UIColor greenColor] size:CGSizeMake(90, 2)];
[self addChild:object2];
object2.position = CGPointMake(self.view.center.x+45, self.view.center.y);

object2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:object2.frame.size];

SKPhysicsJointPin *pinJoint = [SKPhysicsJointPin jointWithBodyA:object1.physicsBody bodyB:object2.physicsBody anchor:self.view.center];
[self.physicsWorld addJoint:pinJoint];

【讨论】：