3D柱状图如何不堆叠显示echarts bar3D配置项内容和展示

去掉堆叠属性，柱子就合在了一起，怎么像普通的柱状图，并列显示

       option = {
            title: {
                text: '3D堆叠柱状图',
                x: 'center'
            },
            calculable : true,
            xAxis3D: {
                type: 'category',
                axisTick: {show: false},
                data: ['2007年', '2008年'],
              name:''
            },
            yAxis3D: {
                type: 'category',
                data: ['']
            },
            zAxis3D: {
                type: 'value'
            },
            grid3D: {
                boxWidth: 200,
                boxDepth: 40,
                axisPointer: {
                    show: false
                },
                light: {
                    main: {
                        intensity: 1.2
                    },
                    ambient: {
                        intensity: 0.3
                    }
                },
                viewControl: {
                    alpha: 10, //控制场景平移旋转
                    beta: 10,
                    distance:300,
                    minAlpha: 10,
                    maxAlpha: 10,
                    minBeta: 10,
                    maxBeta: 200,
                    damping:0.8,
                    rotateMouseButton:'left'
                }
            },
            series: [
                {
                    type: 'bar3D',
                    barSize: 15,
                    data: [
                        [0, 0, 1],
                        [1, 0, 3]
                    ],
                    shading: 'lambert',
                    stack:'stack',
                    emphasis: {
                        label: {
                            show: false
                        }
                    }
                }, {
                    type: 'bar3D',
                    barSize: 15,
                    data: [
                        [0, 0, 5],
                        [1, 0, 4]
                    ],
                    stack:'stack',
                    shading: 'lambert',
                    emphasis: {
                        label: {
                            show: false
                        }
                    }
                }]
        };