SpriteKit代码动态调整sks文件中粒子的颜色

在Xcode中我们可以很方便的使用粒子模板制作粒子,然后保存为sks文件,这样我们随时就可以在代码中使用它们了:

if let fireParticles = SKEmitterNode(fileNamed: "FireParticles"){
    //do anything you want!!!
}

我们想要制作的效果是当小球调入时间空隙时显示被吞噬的粒子效果,不过sks文件中的粒子消逝效果是粉色烟雾的,但是小球有7种颜色:

我当然可以依次制作7个sks粒子文件对应每个球的颜色,但显然这违反了KISS原则.更好的做法是用代码调整不同颜色的小球消逝时产生对应颜色的烟雾,而不是都是粉色滴,那么单调 ;(

我们打开Xcode的粒子编辑器界面,可以发现其中有一个Color Ramp属性:

它对应于粒子对象的particleColor的属性,如果我们直接在代码中修改它可以实现改变粒子颜色吗?答案是:不可以!

原因在此:

The particleColor property isn‘t working because of the color ramp settings in the Particle Editor. These are actually stored in the particleColorSequence, which ignores all other particle color properties.

So, to make it work, you need to override the particleColorSequence setter and make it nil first. Then, you need to set the particleColorBlendFactor to fully blend your chosen color with the particle texture (full blending is 1.0). From then on, any explicit particle color setting should work:

emitter.particleColorSequence = nil;
emitter.particleColorBlendFactor = 1.0;
emitter.particleColor = [SKColor redColor];

各位看官都很清楚了吧?如果少数不明所以的吃瓜群众一脸朦胧状,请跟帖或私信 ;)

上面是Objc的代码,我们把它改为Swift:

//["ballBlue","ballCyan","ballGreen","ballGrey","ballPurple","ballRed","ballYellow"]
    func destroyBall(_ ball:SKNode){

        if let fireParticles = SKEmitterNode(fileNamed: "FireParticles"){
            fireParticles.position = ball.position

            let imageName = ball.userData!["imageName"] as! String
            var particelColor:UIColor
            switch imageName {
            case "ballBlue":
                particelColor = .blue
            case "ballCyan":
                particelColor = .cyan
            case "ballGreen":
                particelColor = .green
            case "ballGrey":
                particelColor = .gray
            case "ballPurple":
                particelColor = .purple
            case "ballRed":
                particelColor = .red
            case "ballYellow":
                particelColor = .yellow
            default:
                fatalError("非法的颜色名称!!!")
            }

            fireParticles.particleColorSequence = nil
            fireParticles.particleColorBlendFactor = 1.0
            fireParticles.particleColor = particelColor

            addChild(fireParticles)
        }

        ball.removeFromParent()
    }

哦了!我们成功的完成了题目的要求(gif动图加载较慢):