January 2020
Intermediate to advanced
356 pages
6h 4m
Chinese
Content preview from Swift游戏开发经典实例
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物理学
｜
239
let explosionOffset =
CGVector(dx: bodyPosition.x - point.x,
dy: bodyPosition.y - point.y)
2.
对
explosionOffset
进行单位化。也就是计算出向量的长度（即大小），然后
将向量除以长度。
要计算向量的长度，可以将向量每条边平方后相加，再开方。
let explosionDistance =
sqrt(explosionOffset.dx * explosionOffset.dx +
explosionOffset.dy * explosionOffset.dy)
然后，将
explosionOffset
除以向量长度，再乘以爆炸威力。这样，所有受影响
的物体都会受到同样的爆炸威力，无论它们的位置远近：
let explosionDistance =
sqrt(explosionOffset.dx * explosionOffset.dx +
explosionOffset.dy * explosionOffset.dy)
3.
最后
,
将计算出的力应用到每个物体：
body.applyForce(explosionForce)
7.17
根据设备方向改变重力
问题
我们要在玩家旋转设备时使重力的方向也发生改变。
解决方案
首先，在项目导航窗口顶部，选中项目名称，在
General
标签页中，拉到“
Device
Orientation
”处，关掉除“
Portaint
”以外的所有选项。这样就保证我们的 ...
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