layers中上面的图层会挡住下面的图层导致无法选中下面图层中的物体echarts 配置项内容和展示

云层会遮挡地球表面图层导致国家无法用鼠标选取，如何才能在保留云层的情况下选中国家？

      var baseTexture = "/asset/get/s/data-1524241630540-ryDJS5P2f.jpg";

var clouds = "/asset/get/s/data-1524241644720-H1rlB5Pnz.png";

var heightTexture = "/asset/get/s/data-1524241653833-S1CgS5vnM.jpg";

//创建canvas贴图
var canvas = document.createElement('canvas');
var mapChart = echarts.init(canvas, null, {
    width: 2048,
    height: 1024
});
mapChart.setOption({
    geo: {
        type: 'map',
        map: 'world',
        top: 0,
        left: 0,
        right: 0,
        bottom: 0,
        boundingCoords: [
            [-180, 90],
            [180, -90]
        ],
        itemStyle: {
            normal: {
                areaColor: 'transparent',
                borderColor: '#121212'
            },
            emphasis: {
                areaColor: 'yellow'
            }
        },
        selectedMode: 'single'
    }
});
var option = {
    backgroundColor: '#000',
    globe: {
        //基本贴图
        baseTexture: baseTexture,
        //高度纹理贴图
        heightTexture: heightTexture,
        //地球顶点位移的大小
        displacementScale: 0.5,
        //地球顶点位移的质量
        displacementQuality: 'high',
        //使用渐变色作为环境色
        environment: new echarts.graphic.LinearGradient(0, 0, 0, 1, [{
            offset: 0,
            color: '#00aaff' // 天空颜色
        }, {
            offset: 0.7,
            color: '#998866' // 地面颜色
        }, {
            offset: 1,
            color: '#998866' // 地面颜色
        }], false),
        //地球中三维图形的着色效果
        shading: 'lambert', //color,lambert,realistic
        light: {
            ambient: {
                intensity: 0.6
            },
            main: {
                intensity: 1.0
            }
        },

        layers: [
            //echarts 4 中type不能为blend，是bug
            {
                type: 'blend',
                texture: mapChart,
                shading: 'lambert',
            },
            //上面的层会挡住下面的层导致无法选中
            {
                type: 'overlay',
                texture: clouds,
                shading: 'lambert',
                distance: 5
            },
        ],
    },
    series: [

    ]
}