使用 Swift 在向下循环中移动 SKSpriteNode [英] Moving a SKSpriteNode in a downward loop, using Swift
问题描述
使用 Swift 和 SpriteKit,我想以螺旋模式移动 SKSpritenode,但没有找到合适的资源来帮助我开始.更准确地说,我想在向下循环中移动精灵节点.我检查了一系列 SKAction,但由于它们不是并行执行的,因此与 move-to 相结合的圆周运动将不起作用.如果有任何提示、教程或片段能让我走上正轨,我会很高兴.
Using Swift and SpriteKit, I'd like to move a SKSpritenode in a spiral pattern, but didn't find the right resources to get me started. To be more precise, I'd like to move a sprite node in a downward loop. I've checked a sequence of SKActions, but as they are not executed parallel, a circular movement combined with move-to will not work. I'd be glad for any hints, tutorials or snippets to set me on the right track.
提前谢谢,马库斯
推荐答案
我整理了一些示例代码,您可以根据自己的目的进行调整.我已经根据 阿基米德螺旋的等式编写了代码:
I've put together some sample code which you can adapt for your purposes. I've based the code off the equation for an Archimedean Spiral:
r = a + bθ
其中a
是起始半径;b
是螺旋每转增加的半径,θ
是当前角度.
Where a
is the starting radius; b
is the radius the spiral will increase by per revolution and θ
is the current angle.
螺旋基本上是一个美化圆 (IMO),因此要在螺旋中移动您的节点,您需要能够使用角度、半径和中心点计算圆上的点:
A spiral is basically a glorified circle (IMO), so to move your node in a spiral you need to be able to calculate point on a circle using an angle, radius and center point:
func pointOnCircle(#angle: CGFloat, #radius: CGFloat, #center: CGPoint) -> CGPoint {
return CGPoint(x: center.x + radius * cos(angle),
y: center.y + radius * sin(angle))
}
接下来,扩展 SKAction
以便您可以轻松创建螺旋动作:
Next, extend SKAction
so you can easily create a spiral action:
extension SKAction {
static func spiral(#startRadius: CGFloat, endRadius: CGFloat, angle
totalAngle: CGFloat, centerPoint: CGPoint, duration: NSTimeInterval) -> SKAction {
// The distance the node will travel away from/towards the
// center point, per revolution.
let radiusPerRevolution = (endRadius - startRadius) / totalAngle
let action = SKAction.customActionWithDuration(duration) { node, time in
// The current angle the node is at.
let θ = totalAngle * time / CGFloat(duration)
// The equation, r = a + bθ
let radius = startRadius + radiusPerRevolution * θ
node.position = pointOnCircle(angle: θ, radius: radius, center: centerPoint)
}
return action
}
}
最后是一个使用示例.在 didMoveToView
中:
Finally, an example of use. In didMoveToView
:
let node = SKSpriteNode(color: UIColor.redColor(), size: CGSize(width: 10, height: 10))
node.position = CGPoint(x: size.width / 2, y: size.height / 2)
addChild(node)
let spiral = SKAction.spiral(startRadius: size.width / 2,
endRadius: 0,
angle: CGFloat(M_PI) * 2,
centerPoint: node.position,
duration: 5.0)
node.runAction(spiral)
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