PrimitiveType.TRIANGLES,
                        boundingSphere: Cesium.BoundingSphere.fromVertices(positions)
                    }),
                    // attributes : {
                    //     color : Cesium.ColorGeometryInstanceAttribute.fromColor(new Cesium.Color(1.0, 1.0, 0.0, 1.0))
                    // }
                }),
                // appearance: new Cesium.PerInstanceColorAppearance({
                //     flat : true,
                //     translucent : false
             