Add existing to tracked

node_modules/@cesium/engine/Source/Scene/Model/LightingModel.js

@@ -0,0 +1,34 @@
+// @ts-check
+
+/**
+ * The lighting model to use for lighting a {@link Model}.
+ *
+ * @enum {number}
+ *
+ * @experimental This feature is using part of the 3D Tiles spec that is not final and is subject to change without Cesium's standard deprecation policy.
+ */
+const LightingModel = {
+  /**
+   * Use unlit shading, i.e. skip lighting calculations. The model's
+   * diffuse color (assumed to be linear RGB, not sRGB) is used directly
+   * when computing <code>out_FragColor</code>. The alpha mode is still
+   * applied.
+   *
+   * @type {number}
+   * @constant
+   */
+  UNLIT: 0,
+  /**
+   * Use physically-based rendering lighting calculations. This includes
+   * both PBR metallic roughness and PBR specular glossiness. Image-based
+   * lighting is also applied when possible.
+   *
+   * @type {number}
+   * @constant
+   */
+  PBR: 1,
+};
+
+Object.freeze(LightingModel);
+
+export default LightingModel;