iOS -- SpriteKit框架之SKPhysicsBody的移动和连接

 

SKPhysicsBody的受力移动

SKPhysicsBody对象不同于SKSpriteNode对象.SKSpriteNode对象可以通过添加动作来进行移动,SKPhysicsBody对象却没有移动这一说法,那么我们该如何移动SKPhysicsBody对象呢?这就需要我们使用到力的作用.用力让物理体产生运动效果.下面我们看一下给物理体添加作用力的方法.

下面我们看看具体的示例,如下所示.

首先我让整个场景的物理世界的重力加速为0,也就是说没有重力加速度.

-(instancetype)initWithSize:(CGSize)size{

    if (self = [super initWithSize:size]) {

        //设置场景的物理世界
        self.physicsWorld.gravity = CGVectorMake(0.0, 0.0);

    }

    return self;
}

接下来就是设置背景和实验体精灵以及场景的边界.代码如下所示.

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

    [self backgroundNode];

    [self planeNode];

    //设置边界
    self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(self.frame.origin.x, self.frame.origin.y, self.size.width, self.size.height)];
}

#pragma mark ----创建背景----

-(void)backgroundNode{

    SKSpriteNode *backgroundNode = [SKSpriteNode spriteNodeWithImageNamed:@"bg_02.jpg"];

    backgroundNode.position = CGPointZero;

    backgroundNode.zPosition = 0;

    backgroundNode.anchorPoint = CGPointZero;

    backgroundNode.size = self.size;

    [self addChild:backgroundNode];



}

#pragma mark ---- 创建飞船 ----

-(void)planeNode{

    SKSpriteNode *planeNode = [SKSpriteNode spriteNodeWithImageNamed:@"飞机.png"];

    planeNode.position = CGPointMake(self.size.width/2, self.size.height/2);

    planeNode.anchorPoint = CGPointMake(0.5, 0.5);

    planeNode.zPosition = 1;

    planeNode.name = @"plane";

    [self addChild:planeNode];


}

下面,我们在touchBegan里面创建物理体,并且给它一个水平向右的1000N拉力.代码如下

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

    SKSpriteNode *planeNode = (SKSpriteNode *)[self childNodeWithName:@"plane"];

    planeNode.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:planeNode.size];

    planeNode.physicsBody.restitution = 0;

    [planeNode.physicsBody applyForce:CGVectorMake(1000, 0)];

}

接下来,小葵花牌妈妈开课了!!!我们就对上面的物理体进行受力分析,我们知道物体受到一个水平向右的1000N拉力,由于线性阻尼没有进行设置,默认为0.2.所以物体同时受到一个水平向左的摩擦力,这样物体就做一个减速运动.

 

我们看一下直接的效果图.

效果图

其他的几个受力情况由于类似,所以这里就不一一说明.

SKPhysicsBody的连接

物理体的连接,其实就是把两个物理体用一定的方式连接在一起.连接方式总共有五种如下图所示.

物理体连接方式

下面我们就以弹簧联合来做一个示例.首先,我们先把准备工作做好.创建场景,在场景中创建两个正方体,代码如下所示.

#import "GameScene.h"

@implementation GameScene

-(instancetype)initWithSize:(CGSize)size{

    if (self = [super initWithSize:size]) {

        self.backgroundColor = [SKColor whiteColor];

//        self.physicsWorld.gravity = CGVectorMake(0, 0);

    }

    return self;
}


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


    [self cubeNode];

    //设置边界
    self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(self.frame.origin.x, self.frame.origin.y, self.size.width, self.size.height)];

}

#pragma mark ----创建两个正方体 --- 

-(void)cubeNode{


    SKSpriteNode *cubeNode = [SKSpriteNode spriteNodeWithImageNamed:@"正方体.png"];

    cubeNode.position = CGPointMake(self.size.width/2, self.size.height/2+200);

    cubeNode.anchorPoint = CGPointMake(0.5, 0.5);

    cubeNode.zPosition = 1;

    cubeNode.name = @"cubeNode";

    [self addChild:cubeNode];



    SKSpriteNode *cubeNode1 = [SKSpriteNode spriteNodeWithImageNamed:@"正方体.png"];

    cubeNode1.position = CGPointMake(self.size.width/2, self.size.height/2);

    cubeNode1.anchorPoint = CGPointMake(0.5, 0.5);

    cubeNode1.zPosition = 1;

    cubeNode1.name = @"cubeNode1";

    [self addChild:cubeNode1];


}

我们依然是在touchBegan方法中进行操作,在方法中,我们个两个正方体节点创建对应的物理体,然后创建两个物理体的弹簧联合方式以及设置联合方式的属性,并且添加到场景的物理世界中.代码如下所示.

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

    SKSpriteNode *cubeNode = (SKSpriteNode *)[self childNodeWithName:@"cubeNode"];

    cubeNode.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:cubeNode.size];

    SKSpriteNode *cubeNode1 = (SKSpriteNode *)[self childNodeWithName:@"cubeNode1"];

    cubeNode1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:cubeNode1.size];

    SKPhysicsJointSpring *springPhysicsJoint = [SKPhysicsJointSpring jointWithBodyA:cubeNode.physicsBody bodyB:cubeNode1.physicsBody anchorA:cubeNode.position anchorB:cubeNode1.position];

    //弹簧的阻尼
    springPhysicsJoint.damping  = 0.2;

    //弹簧的振动频率
    springPhysicsJoint.frequency = 2.0;

    [self.physicsWorld addJoint:springPhysicsJoint];
}

那么,小葵花牌妈妈又开课了,我们看一下下图,一旦touchBegan方法被触发,那么两个物体就会做自由落体运动.掉落到场景的边界之后,反弹,同时弹簧发生振动.由于摩擦力的存在,最后,全部静止.不懂的童鞋可以去看下高中的物理必修一,力那一章??.

 

整体的效果图如下.

效果图

好了,SKPhysicsBody的移动和连接就说到这了,希望这篇SKPhysicsBody的移动和连接能对您有所帮助.最后双手奉上SKPhysicsBody的移动和连接的Demo.这里是整合版吆~

-->SKPhysicsBody的移动和连接Demo ??