SKPhysicsBody和[SKNode setScale：] [英] SKPhysicsBody and [SKNode setScale:]

问题描述

在我目前使用SpriteKit的项目中，我有一堆精灵需要在不同的时间独立地放大和缩小。问题在于，当我缩放节点时，物理体不会随之缩放，因此它会破坏物理学。这是我为了这个问题而放在一起的一个小例子：

In my current project using SpriteKit, I have a bunch of sprites that need to be scaled up and down independently at various times. The problem is that when I scale the node, the physics body doesn't scale with it so it screws up the physics. Here's a small example I put together for the purpose of this question:

CGSize objectSize = CGSizeMake(100, 100);
self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:CGRectMake(0, 0, self.size.width, self.size.height)];

SKSpriteNode *n1 = [SKSpriteNode spriteNodeWithColor:[UIColor blueColor] size:objectSize];
n1.position = CGPointMake(self.size.width/2, 2*self.size.height/3);
n1.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:objectSize];
n1.physicsBody.affectedByGravity = YES;
[self addChild:n1];

SKSpriteNode *n2 = [SKSpriteNode spriteNodeWithColor:[UIColor redColor] size:objectSize];
n2.position = CGPointMake(self.size.width/2, self.size.height/3);
n2.physicsBody = [SKPhysicsBody bodyWithRectangleOfSize:objectSize];
n2.physicsBody.affectedByGravity = YES;
[self addChild:n2];

[n1 setScale:0.5];

注意蓝色精灵（按比例缩小）如何位于红色精灵之上，但你可以告诉它的物理身体仍然有维度我告诉它，它没有扩展。

Notice how the blue sprite (scaled down) sits on top of the red one but you can tell its physics body still has the dimension I told it, and it didn't scale.

很明显，缩小节点不会缩小物理范围。所以我的问题是如果我必须手动完成它，我该怎么做呢？

So obviously, scaling down the node doesn't scale down the physicsBody. So my question is if I have to manually do it, how do I go about it?

我尝试在缩放时用正确的尺寸交换身体，但是然后如果旧的身体有关节等，事情会变得非常复杂......如果我能以某种方式缩放现有的身体，那就简单多了。

I tried swapping the body with one of the right size when scaling, but then things get really convoluted if the old body had joints, etc... It'd be a lot simpler if I could just scale the existing body somehow.

推荐答案

使用 SKAction 或更新循环，您可以创建一个新的 SKPhysicsBody 适当的比例并将其应用于对象。但是，通过这样做，您将失去速度。要解决此问题，您可以执行以下操作：

Using either an SKAction or the Update loop, you can create a new SKPhysicsBody with the proper scale and apply it to the object. However, by doing so, you will lose the velocity. To fix this, you can do the following:

SKPhysicsBody *newBody = [SKPhysicsBody bodyWithRectangleOfSize:boxObject.size];
newBody.velocity = boxObject.physicsBody.velocity;

boxObject.physicsBody = newBody;

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