如何从 SKTextureAtlas 为 SKPhysicsBody 纹理设置动画答案

【问题标题】：How can I animate a SKPhysicsBody texture from an SKTextureAtlas如何从 SKTextureAtlas 为 SKPhysicsBody 纹理设置动画
【发布时间】：2019-01-07 04:05:36
【问题描述】：

我有一个 SKTextureAtlas，其中包含 7 帧具有透明背景的动画精灵。

我已经能够使用图集中的单个帧作为物理体的边界，但我想知道，如果可能的话，如何让物理体为图集中的每一帧更新其轮廓.

这里我有使用名为“Run0”的框架的物理体，并且它被正确应用。我只是想看看这是否可能，或者让物理体使用图集中从“Run0”到“Run7”的每一帧是否完全不切实际。

Image of physics body with the outline of "Run0"

这是我正在处理的代码：

import SpriteKit

类 GameScene：SKScene {

let dogSpriteNode = SKSpriteNode(imageNamed: "Run0")
var dogFrames = [SKTexture]()

override func didMove(to view: SKView) {

    physicsWorld.gravity = CGVector(dx: 0, dy: -9.8)
    physicsBody = SKPhysicsBody(edgeLoopFrom: frame)

    dogSpriteNode.setScale(0.1)
    dogSpriteNode.position = CGPoint(x: frame.midX, y: frame.midY)
    addChild(dogSpriteNode)

    let textureAtlas = SKTextureAtlas(named: "Dog Frames")

    for index in 0..<textureAtlas.textureNames.count {
        let textureName = "Run" + String(index)
        dogFrames.append(textureAtlas.textureNamed(textureName))
    }

    dogSpriteNode.physicsBody = SKPhysicsBody(
        texture: textureAtlas.textureNamed("Run0"),
        alphaThreshold: 0.5,
        size: dogSpriteNode.frame.size)

}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

    dogSpriteNode.run(SKAction.group([SKAction.repeatForever(SKAction.animate(with: dogFrames, timePerFrame: 0.1))]))
    dogSpriteNode.run(SKAction.applyImpulse(CGVector(dx: 0, dy: 1000), duration: 0.1))

}

}

【问题讨论】：

标签： ios swift sprite-kit skphysicsbody sktextureatlas

【解决方案1】：

实现此目的的一种方法是使用自定义SKAction：

extension SKAction {

    public class func animateTexturesWithPhysics(_ frames: [(texture: SKTexture, duration: TimeInterval)], repeatForever: Bool=true) -> SKAction {
        var actions: [SKAction] = []
        for frame in frames {
            // define a custom action for each frame
            let customAction = SKAction.customAction(withDuration: frame.duration) { node, _ in
                // if the action target is a sprite node, apply the texture & physics
                if node is SKSpriteNode {
                    let setTextureGroup = SKAction.group([
                            SKAction.setTexture(frame.texture, resize: false),
                            SKAction.wait(forDuration: frame.duration),
                            SKAction.run {
                                node.physicsBody = SKPhysicsBody(texture: frame.texture, alphaThreshold: 0.5, size: frame.texture.size())
                                // add physics attributes here
                            }
                        ])
                    node.run(setTextureGroup)
                }
            }
            actions.append(customAction)
        }

        // add the repeating action
        if (repeatForever == true) {
            return SKAction.repeatForever(SKAction.sequence(actions))
        }
        return SKAction.sequence(actions)
    }
}

要实现它，您需要创建一个由帧 + 持续时间组成的数组并将动作应用到精灵：

typealias Frame = (texture: SKTexture, duration: TimeInterval)
let timePerFrame: TimeInterval = 0.1
let dogFrames: [Frame] = dogTextures.map {
    return ($0, timePerFrame)
}

dogSpriteNode = SKSpriteNode(texture: dogFrames.first)
let dogAnimationAction = SKAction.animateTexturesWithPhysics(dogFrames)
dogSpriteNode.run(dogAnimationAction)

【讨论】：