cesium使用primitive添加模型 ，写出实现代码

可以使用以下代码实现cesium使用primitive添加模型：

var viewer = new Cesium.Viewer('cesiumContainer');

var primitive = new Cesium.Primitive({
    geometryInstances: new Cesium.GeometryInstance({
        geometry: new Cesium.BoxGeometry({
            dimensions: new Cesium.Cartesian3(400000., 300000., 500000.)
        }),
        modelMatrix: Cesium.Matrix4.multiplyByTranslation(
            Cesium.Transforms.eastNorthUpToFixedFrame(
                Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883)),
            new Cesium.Cartesian3(., ., 250000.),
            new Cesium.Matrix4()
        ),
        attributes: {
            color: Cesium.ColorGeometryInstanceAttribute.fromColor(Cesium.Color.RED)
        }
    }),
    appearance: new Cesium.PerInstanceColorAppearance()
});

viewer.scene.primitives.add(primitive);

希望对你有帮助！