Cesium添加水面

var viewer = new Cesium.Viewer('cesiumContainer');
var waterPrimitive = new Cesium.Primitive({
        //show:false,// 默认隐藏
        allowPicking:false,
        geometryInstances : new Cesium.GeometryInstance({
            geometry : new Cesium.PolygonGeometry({
                polygonHierarchy : new Cesium.PolygonHierarchy(Cesium.Cartesian3.fromDegreesArrayHeights(waterFace)),//waterFace是一个组成多边形顶点数组[lon,lat,alt]
                //extrudedHeight: 0,//注释掉此属性可以只显示水面
                perPositionHeight : true//注释掉此属性水面就贴地了
            })
        }),
        // 可以设置内置的水面shader
        appearance : new Cesium.EllipsoidSurfaceAppearance({
            material : new Cesium.Material({
                fabric : {
                    type : 'Water',
                    uniforms : {
                        //baseWaterColor:new Cesium.Color(0.0, 0.0, 1.0, 0.5),
                        //blendColor: new Cesium.Color(0.0, 0.0, 1.0, 0.5),
                        //specularMap: 'gray.jpg',
                        normalMap: 'waterNormals.jpg',
                        frequency: 1000.0,
                        animationSpeed: 0.01,
                        amplitude: 10.0
                    }
                }
            }),
            fragmentShaderSource:'varying vec3 v_positionMC;
varying vec3 v_positionEC;
varying vec2 v_st;
void main()
{
czm_materialInput materialInput;
vec3 normalEC = normalize(czm_normal3D * czm_geodeticSurfaceNormal(v_positionMC, vec3(0.0), vec3(1.0)));
#ifdef FACE_FORWARD
normalEC = faceforward(normalEC, vec3(0.0, 0.0, 1.0), -normalEC);
#endif
materialInput.s = v_st.s;
materialInput.st = v_st;
materialInput.str = vec3(v_st, 0.0);
materialInput.normalEC = normalEC;
materialInput.tangentToEyeMatrix = czm_eastNorthUpToEyeCoordinates(v_positionMC, materialInput.normalEC);
vec3 positionToEyeEC = -v_positionEC;
materialInput.positionToEyeEC = positionToEyeEC;
czm_material material = czm_getMaterial(materialInput);
#ifdef FLAT
gl_FragColor = vec4(material.diffuse + material.emission, material.alpha);
#else
gl_FragColor = czm_phong(normalize(positionToEyeEC), material);
                                gl_FragColor.a=0.5;
#endif
}
'//重写shader，修改水面的透明度
        })
    });
water=viewer.scene.primitives.add(waterPrimitive);