solving texture material in forgeViewer, so it is completely unlit (no weird lighting artifacts

unlit-texture.js

function getFlatTexture_FlatMaterial(textureUrl) {
    const shader = {
        side: THREE.DoubleSide,
        depthWrite: false,
        depthTest: true,
        uniforms: {
            map: { value: THREE.ImageUtils.loadTexture(textureUrl),  type: 't' }
        },
        fragmentShader: `
            varying vec2 vUv;
            uniform sampler2D map;

            void main() {
                vec4 texelColor = texture2D( map, vUv );
                gl_FragColor = pow( texelColor, vec4( float( 2.2 ) ) ) ;
            }`,
        vertexShader: `
            varying vec2 vUv;

            void main() {
                vUv = uv;
                gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1.0);
            }`,
    };
    return new THREE.ShaderMaterial(shader);
}


quad(x,y) {
    const szTextureURL = `https://api.mapbox.com/v4/mapbox.satellite/16/${59157+x}/${40217-y}.webp?sku=101gdtmdKGvJF&access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4M29iazA2Z2gycXA4N2pmbDZmangifQ.-g_vE53SD2WrJ6tFX7QHmA`;
    const material = getFlatTexture_FlatMaterial(szTextureURL);
    const mesh = new THREE.Mesh( new THREE.PlaneBufferGeometry( 256, 256 ), material );
    mesh.position.set (x*256,y*256, 1);
    return mesh;
}

const options = {
    env: 'AutodeskProduction',
    accessToken: _access_token,
};
    
Autodesk.Viewing.Initializer(options, () => {
  let viewer = new Autodesk.Viewing.Private.GuiViewer3D(document.getElementById('forgeViewer'));

  // this line is important...
  viewer.start( null, null, null, null, {useIdBufferSelection:true} );

  Autodesk.Viewing.Document.load(`urn:${urn}`, (doc) => {
      var viewables = doc.getRoot().getDefaultGeometry();
      viewer.loadDocumentNode(doc, viewables).then( onLoadFinished );
  });

  function onLoadFinished() {
    viewer.overlays.addScene('map');
    viewer.overlays.addMesh(this.quad(0,0), 'map');
    viewer.overlays.addMesh(this.quad(0,1), 'map');
  };

};