How to add image texture to no texture model

How to add image texture to no texture model?

like this,but Don’t work :
var viewer =initCesium.initViewer(‘cesiumContainer’);
var scene = viewer.scene;

var imagePath = '../data/models/CesiumBalloon/CesiumBalloonPrint_singleDot.png';
var model = createModel('../data/models/ShadowTester/Shadow_Tester_4.gltf');

function createModel(url) {
var origin = Cesium.Cartesian3.fromDegrees(-123.0744619, 44.0503706, 0.0);
var modelMatrix = Cesium.Transforms.headingPitchRollToFixedFrame(origin, new Cesium.HeadingPitchRoll(0.0, 0.0, 0.0));

    var model = scene.primitives.add(Cesium.Model.fromGltf({
        url : url,
        modelMatrix : modelMatrix,
        minimumPixelSize : 128,
        incrementallyLoadTextures : false
    }));

    model.readyPromise.then(function(model) {
        var camera = viewer.camera;

        // Zoom to model
        var controller = scene.screenSpaceCameraController;
        var r = 2.0 * Math.max(model.boundingSphere.radius, camera.frustum.near);
        controller.minimumZoomDistance = r * 0.5;

        var center = Cesium.Matrix4.multiplyByPoint(model.modelMatrix, model.boundingSphere.center, new Cesium.Cartesian3());
        var heading = Cesium.Math.toRadians(230.0);
        var pitch = Cesium.Math.toRadians(-20.0);
        camera.lookAt(center, new Cesium.HeadingPitchRange(heading, pitch, r * 2.0));
    }).otherwise(function(error){
        window.alert(error);
    });

    return model;
}

// Alernate approach - but requires fix in DelayLoadedTextureUniform to return this._textures[this._textureId] instead of this._value
model.readyPromise.then(function() {
var textureIndexToReplace = 0;
var textures = model._rendererResources.textures;
var oldTexture = textures[textureIndexToReplace];
// model.color = Cesium.Color.RED;
// saveJSON(model)
Cesium.Resource.fetchImage({
url : imagePath
}).then(function(image) {
image.width = oldTexture.width
image.height = oldTexture.height
var newTexture = new Cesium.Texture({
context : viewer.scene.frameState.context,
source : image
});

        // oldTexture.destroy();
        textures[textureIndexToReplace] = newTexture;
        newTexture.copyFrom(image);
        newTexture.generateMipmap();
    });
});

image

image

Shadow_Tester_4.gltf (115.4 KB)