Add existing to tracked

node_modules/@cesium/engine/Source/Scene/SceneMode.js

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+/**
+ * Indicates if the scene is viewed in 3D, 2D, or 2.5D Columbus view.
+ *
+ * @enum {number}
+ * @see Scene#mode
+ */
+const SceneMode = {
+  /**
+   * Morphing between mode, e.g., 3D to 2D.
+   *
+   * @type {number}
+   * @constant
+   */
+  MORPHING: 0,
+
+  /**
+   * Columbus View mode.  A 2.5D perspective view where the map is laid out
+   * flat and objects with non-zero height are drawn above it.
+   *
+   * @type {number}
+   * @constant
+   */
+  COLUMBUS_VIEW: 1,
+
+  /**
+   * 2D mode.  The map is viewed top-down with an orthographic projection.
+   *
+   * @type {number}
+   * @constant
+   */
+  SCENE2D: 2,
+
+  /**
+   * 3D mode.  A traditional 3D perspective view of the globe.
+   *
+   * @type {number}
+   * @constant
+   */
+  SCENE3D: 3,
+};
+
+/**
+ * Returns the morph time for the given scene mode.
+ *
+ * @param {SceneMode} value The scene mode
+ * @returns {number} The morph time
+ */
+SceneMode.getMorphTime = function (value) {
+  if (value === SceneMode.SCENE3D) {
+    return 1.0;
+  } else if (value === SceneMode.MORPHING) {
+    return undefined;
+  }
+  return 0.0;
+};
+
+Object.freeze(SceneMode);
+
+export default SceneMode;