使用自定义 SKAction 的 EaseOut 操作

我有以下自定义 SKAction 工作，但作为 EaseIn 而不是 EaseOut。我想让它缓出！我使用网络上找到的各种缓动方程来纠正它，却惨遭失败。

    let duration = 2.0
    let initialX = cameraNode.position.x
    let customEaseOut = SKAction.customActionWithDuration(duration, actionBlock: {node, elapsedTime in

        let t = Double(elapsedTime)/duration
        let b = Double(initialX)
        let c = Double(targetPoint.x)
        let p = t*t*t*t*t

        let l = b*(1-p) + c*p

        node.position.x = CGFloat(l)
    })

    cameraNode.runAction(customEaseOut)

任何帮助将不胜感激。

Thanks

你不需要计算它。

SKAction只是有一个名为timingMode:

// fall is an SKAction
fall.timingMode = .easeInEaseOut

您可以选择：

• 线性（默认）
• easeIn
• easeOut
• 缓进缓出

检查详细信息API docs https://developer.apple.com/reference/spritekit/skaction/1417807-timingmode并且here https://developer.apple.com/reference/spritekit/skactiontimingmode.

如果您需要更改 Apple 预设，您可以使用：定时功能 https://developer.apple.com/reference/spritekit/skactiontimingfunction

fall.timingFunction = { time -> Float in
    return time
}

根据源代码构建自定义函数：

/**
 A custom timing function for SKActions. Input time will be linear 0.0-1.0
 over the duration of the action. Return values must be 0.0-1.0 and increasing
 and the function must return 1.0 when the input time reaches 1.0.
 */
public typealias SKActionTimingFunction = (Float) -> Float

因此，有了这些信息，你可以写：

func CubicEaseOut(_ t:Float)->Float
{
   let f:Float = (t - 1);
   return f * f * f + 1;
}
fall.timingFunction = CubicEaseOut