简单的椭圆效果

const {ccclass, property} = cc._decorator;

let NodeItems = new Array();

@ccclass
export default class EffectOval extends cc.Component {
    // LIFE-CYCLE CALLBACKS:

    @property(cc.Node)
    NodeItem : cc.Node;

    /** 轴长a */
    @property
    a : number = 100;

    /** 轴长b */
    @property
    b : number = 200;

    onLoad () {
        this.NodeItem.active = false;
    }

    start () {
        this.DrawOval();
    }

    /**
     * 获取椭圆上的坐标
     *
     * @param {*} angle
     * @returns
     * @memberof EffectOval
     */
    GetOvalPosition(angle){
        if(angle >= 360){
            angle -= 360;
        }
        console.log("angle",angle);
        let pos = cc.v2(0,0);
        let tan = Math.tan(angle * 3.1415926 / 180);
        pos.x = Math.sqrt(1.0/((1.0/Math.pow(tan,2))*(1.0/Math.pow(this.a,2))+(1.0/Math.pow(this.b,2))));
        pos.y = Math.sqrt(1.0/(1.0/(Math.pow(this.a,2))+Math.pow(tan,2)*(1.0/Math.pow(this.b,2))));

        if (angle < 90 || angle > 270){
            pos.y = -pos.y;
        }
        if (angle > 180){
            pos.x = -pos.x;
        }
        return pos;
    }

    /**
     * 画椭圆
     *
     * @memberof EffectOval
     */
    DrawOval(){
        for(let i = 0;i < 360;){
            let item = cc.instantiate(this.NodeItem);
            item.active = true;
            this.node.addChild(item);
            item.position = this.GetOvalPosition(i);
            let data = {
                item : item,
                angle :i
            }
            NodeItems.push(data);

            i += 20;
        }
    }

    update (dt) {
        for(let i = 0;i < NodeItems.length;++i){
            NodeItems[i].angle += dt * 10;
            NodeItems[i].item.position = this.GetOvalPosition(NodeItems[i].angle);
        }
    }
}