@cesium/engine/Source/Scene/Cesium3DTile.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

import BoundingSphere from "../Core/BoundingSphere.js";
import Cartesian3 from "../Core/Cartesian3.js";
import Color from "../Core/Color.js";
import ColorGeometryInstanceAttribute from "../Core/ColorGeometryInstanceAttribute.js";
import CullingVolume from "../Core/CullingVolume.js";
import defined from "../Core/defined.js";
import deprecationWarning from "../Core/deprecationWarning.js";
import destroyObject from "../Core/destroyObject.js";
import Ellipsoid from "../Core/Ellipsoid.js";
import Intersect from "../Core/Intersect.js";
import JulianDate from "../Core/JulianDate.js";
import CesiumMath from "../Core/Math.js";
import Matrix3 from "../Core/Matrix3.js";
import Matrix4 from "../Core/Matrix4.js";
import OrientedBoundingBox from "../Core/OrientedBoundingBox.js";
import OrthographicFrustum from "../Core/OrthographicFrustum.js";
import Rectangle from "../Core/Rectangle.js";
import Request from "../Core/Request.js";
import RequestScheduler from "../Core/RequestScheduler.js";
import RequestState from "../Core/RequestState.js";
import RequestType from "../Core/RequestType.js";
import Resource from "../Core/Resource.js";
import RuntimeError from "../Core/RuntimeError.js";
import Cesium3DContentGroup from "./Cesium3DContentGroup.js";
import Cesium3DTileContentFactory from "./Cesium3DTileContentFactory.js";
import Cesium3DTileContentState from "./Cesium3DTileContentState.js";
import Cesium3DTileContentType from "./Cesium3DTileContentType.js";
import Cesium3DTileOptimizationHint from "./Cesium3DTileOptimizationHint.js";
import Cesium3DTilePass from "./Cesium3DTilePass.js";
import Cesium3DTileRefine from "./Cesium3DTileRefine.js";
import Empty3DTileContent from "./Empty3DTileContent.js";
import findContentMetadata from "./findContentMetadata.js";
import findGroupMetadata from "./findGroupMetadata.js";
import findTileMetadata from "./findTileMetadata.js";
import hasExtension from "./hasExtension.js";
import Multiple3DTileContent from "./Multiple3DTileContent.js";
import BoundingVolumeSemantics from "./BoundingVolumeSemantics.js";
import preprocess3DTileContent from "./preprocess3DTileContent.js";
import SceneMode from "./SceneMode.js";
import TileBoundingRegion from "./TileBoundingRegion.js";
import TileBoundingS2Cell from "./TileBoundingS2Cell.js";
import TileBoundingSphere from "./TileBoundingSphere.js";
import TileOrientedBoundingBox from "./TileOrientedBoundingBox.js";
import Pass from "../Renderer/Pass.js";
import VerticalExaggeration from "../Core/VerticalExaggeration.js";

/**
 * A tile in a {@link Cesium3DTileset}.  When a tile is first created, its content is not loaded;
 * the content is loaded on-demand when needed based on the view.
 * <p>
 * Do not construct this directly, instead access tiles through {@link Cesium3DTileset#tileVisible}.
 * </p>
 *
 * @alias Cesium3DTile
 * @constructor
 * @param {Cesium3DTileset} tileset The tileset
 * @param {Resource} baseResource The base resource for the tileset
 * @param {object} header The JSON header for the tile
 * @param {Cesium3DTile} parent The parent tile of the new tile
 */
function Cesium3DTile(tileset, baseResource, header, parent) {
  this._tileset = tileset;
  this._header = header;

  const hasContentsArray = defined(header.contents);
  const hasMultipleContents =
    (hasContentsArray && header.contents.length > 1) ||
    hasExtension(header, "3DTILES_multiple_contents");

  // In the 1.0 schema, content is stored in tile.content instead of tile.contents
  const contentHeader =
    hasContentsArray && !hasMultipleContents
      ? header.contents[0]
      : header.content;

  this._contentHeader = contentHeader;

  /**
   * The local transform of this tile.
   * @type {Matrix4}
   */
  this.transform = defined(header.transform)
    ? Matrix4.unpack(header.transform)
    : Matrix4.clone(Matrix4.IDENTITY);

  const parentTransform = defined(parent)
    ? parent.computedTransform
    : tileset.modelMatrix;
  const computedTransform = Matrix4.multiply(
    parentTransform,
    this.transform,
    new Matrix4(),
  );

  const parentInitialTransform = defined(parent)
    ? parent._initialTransform
    : Matrix4.IDENTITY;
  this._initialTransform = Matrix4.multiply(
    parentInitialTransform,
    this.transform,
    new Matrix4(),
  );

  /**
   * The final computed transform of this tile.
   * @type {Matrix4}
   * @readonly
   */
  this.computedTransform = computedTransform;

  /**
   * When tile metadata is present (3D Tiles 1.1) or the <code>3DTILES_metadata</code> extension is used,
   * this stores a {@link TileMetadata} object for accessing tile metadata.
   *
   * @type {TileMetadata}
   * @readonly
   * @private
   * @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.
   */
  this.metadata = findTileMetadata(tileset, header);

  this._verticalExaggeration = 1.0;
  this._verticalExaggerationRelativeHeight = 0.0;

  // Important: tile metadata must be parsed before this line so that the
  // metadata semantics TILE_BOUNDING_BOX, TILE_BOUNDING_REGION, or TILE_BOUNDING_SPHERE
  // can override header.boundingVolume (if necessary)
  this._boundingVolume = this.createBoundingVolume(
    header.boundingVolume,
    computedTransform,
  );
  this._boundingVolume2D = undefined;

  let contentBoundingVolume;

  if (defined(contentHeader) && defined(contentHeader.boundingVolume)) {
    // Non-leaf tiles may have a content bounding-volume, which is a tight-fit bounding volume
    // around only the features in the tile.  This box is useful for culling for rendering,
    // but not for culling for traversing the tree since it does not guarantee spatial coherence, i.e.,
    // since it only bounds features in the tile, not the entire tile, children may be
    // outside of this box.
    contentBoundingVolume = this.createBoundingVolume(
      contentHeader.boundingVolume,
      computedTransform,
    );
  }
  this._contentBoundingVolume = contentBoundingVolume;
  this._contentBoundingVolume2D = undefined;

  let viewerRequestVolume;
  if (defined(header.viewerRequestVolume)) {
    viewerRequestVolume = this.createBoundingVolume(
      header.viewerRequestVolume,
      computedTransform,
    );
  }
  this._viewerRequestVolume = viewerRequestVolume;

  /**
   * The error, in meters, introduced if this tile is rendered and its children are not.
   * This is used to compute screen space error, i.e., the error measured in pixels.
   *
   * @type {number}
   * @readonly
   */
  this.geometricError = header.geometricError;
  this._geometricError = header.geometricError;

  if (!defined(this._geometricError)) {
    this._geometricError = defined(parent)
      ? parent._geometricError
      : tileset._geometricError;
    Cesium3DTile._deprecationWarning(
      "geometricErrorUndefined",
      "Required property geometricError is undefined for this tile. Using parent's geometric error instead.",
    );
  }

  this.updateGeometricErrorScale();

  let refine;
  if (defined(header.refine)) {
    if (header.refine === "replace" || header.refine === "add") {
      Cesium3DTile._deprecationWarning(
        "lowercase-refine",
        `This tile uses a lowercase refine "${
          header.refine
        }". Instead use "${header.refine.toUpperCase()}".`,
      );
    }
    refine =
      header.refine.toUpperCase() === "REPLACE"
        ? Cesium3DTileRefine.REPLACE
        : Cesium3DTileRefine.ADD;
  } else if (defined(parent)) {
    // Inherit from parent tile if omitted.
    refine = parent.refine;
  } else {
    refine = Cesium3DTileRefine.REPLACE;
  }

  /**
   * Specifies the type of refinement that is used when traversing this tile for rendering.
   *
   * @type {Cesium3DTileRefine}
   * @readonly
   * @private
   */
  this.refine = refine;

  /**
   * Gets the tile's children.
   *
   * @type {Cesium3DTile[]}
   * @readonly
   */
  this.children = [];

  /**
   * This tile's parent or <code>undefined</code> if this tile is the root.
   * <p>
   * When a tile's content points to an external tileset JSON file, the external tileset's
   * root tile's parent is not <code>undefined</code>; instead, the parent references
   * the tile (with its content pointing to an external tileset JSON file) as if the two tilesets were merged.
   * </p>
   *
   * @type {Cesium3DTile}
   * @readonly
   */
  this.parent = parent;

  let content;
  let hasEmptyContent = false;
  let contentState;
  let contentResource;
  let serverKey;

  baseResource = Resource.createIfNeeded(baseResource);

  if (hasMultipleContents) {
    contentState = Cesium3DTileContentState.UNLOADED;
    // Each content may have its own URI, but they all need to be resolved
    // relative to the tileset, so the base resource is used.
    contentResource = baseResource.clone();
  } else if (defined(contentHeader)) {
    let contentHeaderUri = contentHeader.uri;
    if (defined(contentHeader.url)) {
      Cesium3DTile._deprecationWarning(
        "contentUrl",
        'This tileset JSON uses the "content.url" property which has been deprecated. Use "content.uri" instead.',
      );
      contentHeaderUri = contentHeader.url;
    }
    if (contentHeaderUri === "") {
      Cesium3DTile._deprecationWarning(
        "contentUriEmpty",
        "content.uri property is an empty string, which creates a circular dependency, making this tileset invalid. Omit the content property instead",
      );
      content = new Empty3DTileContent(tileset, this);
      hasEmptyContent = true;
      contentState = Cesium3DTileContentState.READY;
    } else {
      contentState = Cesium3DTileContentState.UNLOADED;
      contentResource = baseResource.getDerivedResource({
        url: contentHeaderUri,
      });
      serverKey = RequestScheduler.getServerKey(
        contentResource.getUrlComponent(),
      );
    }
  } else {
    content = new Empty3DTileContent(tileset, this);
    hasEmptyContent = true;
    contentState = Cesium3DTileContentState.READY;
  }

  this._content = content;
  this._contentResource = contentResource;
  this._contentState = contentState;
  this._expiredContent = undefined;

  this._serverKey = serverKey;

  /**
   * When <code>true</code>, the tile has no content.
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  this.hasEmptyContent = hasEmptyContent;

  /**
   * When <code>true</code>, the tile's content points to an external tileset.
   * <p>
   * This is <code>false</code> until the tile's content is loaded.
   * </p>
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  this.hasTilesetContent = false;

  /**
   * When <code>true</code>, the tile's content is an implicit tileset.
   * <p>
   * This is <code>false</code> until the tile's implicit content is loaded.
   * </p>
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   * @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.
   */
  this.hasImplicitContent = false;

  /**
   * Determines whether the tile has renderable content.
   *
   * The loading starts with the assumption that the tile does have
   * renderable content, if the content is not empty.<br>
   * <br>
   * This turns <code>false</code> only when the tile content is loaded
   * and turns out to be a single content that points to an external
   * tileset or implicit content
   * </p>
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  this.hasRenderableContent = !hasEmptyContent;

  /**
   * When <code>true</code>, the tile contains content metadata from implicit tiling. This flag is set
   * for tiles transcoded by <code>Implicit3DTileContent</code>.
   * <p>
   * This is <code>false</code> until the tile's content is loaded.
   * </p>
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   * @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.
   */
  this.hasImplicitContentMetadata = false;

  /**
   * When <code>true</code>, the tile has multiple contents, either in the tile JSON (3D Tiles 1.1)
   * or via the <code>3DTILES_multiple_contents</code> extension.
   *
   * @see {@link https://github.com/CesiumGS/3d-tiles/tree/main/extensions/3DTILES_multiple_contents|3DTILES_multiple_contents extension}
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  this.hasMultipleContents = hasMultipleContents;

  /**
   * The node in the tileset's LRU cache, used to determine when to unload a tile's content.
   *
   * See {@link Cesium3DTilesetCache}
   *
   * @type {DoublyLinkedListNode}
   * @readonly
   *
   * @private
   */
  this.cacheNode = undefined;

  const expire = header.expire;
  let expireDuration;
  let expireDate;
  if (defined(expire)) {
    expireDuration = expire.duration;
    if (defined(expire.date)) {
      expireDate = JulianDate.fromIso8601(expire.date);
    }
  }

  /**
   * The time in seconds after the tile's content is ready when the content expires and new content is requested.
   *
   * @type {number}
   */
  this.expireDuration = expireDuration;

  /**
   * The date when the content expires and new content is requested.
   *
   * @type {JulianDate}
   */
  this.expireDate = expireDate;

  /**
   * The time when a style was last applied to this tile.
   *
   * @type {number}
   *
   * @private
   */
  this.lastStyleTime = 0.0;

  /**
   * Marks whether the tile's children bounds are fully contained within the tile's bounds
   *
   * @type {Cesium3DTileOptimizationHint}
   *
   * @private
   */
  this._optimChildrenWithinParent = Cesium3DTileOptimizationHint.NOT_COMPUTED;

  /**
   * Tracks if the tile's relationship with a ClippingPlaneCollection has changed with regards
   * to the ClippingPlaneCollection's state.
   *
   * @type {boolean}
   *
   * @private
   */
  this.clippingPlanesDirty = false;

  /**
   * Tracks if the tile's relationship with a ClippingPolygonCollection has changed with regards
   * to the ClippingPolygonCollection's state.
   *
   * @type {boolean}
   *
   * @private
   */
  this.clippingPolygonsDirty = false;

  /**
   * Tracks if the tile's request should be deferred until all non-deferred
   * tiles load.
   *
   * @type {boolean}
   *
   * @private
   */
  this.priorityDeferred = false;

  /**
   * For implicit tiling, an ImplicitTileset object will be attached to a
   * placeholder tile with either implicit tiling in the JSON (3D Tiles 1.1)
   * or the <code>3DTILES_implicit_tiling</code> extension.
   * This way the {@link Implicit3DTileContent} can access the tile later once the content is fetched.
   *
   * @type {ImplicitTileset|undefined}
   *
   * @private
   * @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.
   */
  this.implicitTileset = undefined;

  /**
   * For implicit tiling, the (level, x, y, [z]) coordinates within the
   * implicit tileset are stored in the tile.
   *
   * @type {ImplicitTileCoordinates|undefined}
   *
   * @private
   * @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.
   */
  this.implicitCoordinates = undefined;

  /**
   * For implicit tiling, each transcoded tile will hold a weak reference to
   * the {@link ImplicitSubtree}.
   *
   * @type {ImplicitSubtree|undefined}
   *
   * @private
   * @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.
   */
  this.implicitSubtree = undefined;

  // Members that are updated every frame for tree traversal and rendering optimizations:
  this._distanceToCamera = 0.0;
  this._centerZDepth = 0.0;
  this._screenSpaceError = 0.0;
  this._screenSpaceErrorProgressiveResolution = 0.0; // The screen space error at a given screen height of tileset.progressiveResolutionHeightFraction * screenHeight
  this._visibilityPlaneMask = 0;
  this._visible = false;
  this._inRequestVolume = false;

  this._finalResolution = true;
  this._depth = 0;
  this._stackLength = 0;
  this._selectionDepth = 0;

  this._updatedVisibilityFrame = 0;
  this._touchedFrame = 0;
  this._visitedFrame = 0;
  this._selectedFrame = 0;
  this._wasSelectedLastFrame = false;
  this._requestedFrame = 0;
  this._ancestorWithContent = undefined;
  this._ancestorWithContentAvailable = undefined;
  this._refines = false;
  this._shouldSelect = false;
  this._isClipped = true;
  this._isClippedByPolygon = false;
  this._clippingPlanesState = 0; // encapsulates (_isClipped, clippingPlanes.enabled) and number/function
  this._clippingPolygonsState = 0; // encapsulates (_isClipped, clippingPolygons.enabled) and number/function
  this._debugBoundingVolume = undefined;
  this._debugContentBoundingVolume = undefined;
  this._debugViewerRequestVolume = undefined;
  this._debugColor = Color.fromRandom({ alpha: 1.0 });
  this._debugColorizeTiles = false;

  this._priority = 0.0; // The priority used for request sorting
  this._priorityHolder = this; // Reference to the ancestor up the tree that holds the _foveatedFactor and _distanceToCamera for all tiles in the refinement chain.
  this._priorityProgressiveResolution = false;
  this._priorityProgressiveResolutionScreenSpaceErrorLeaf = false;
  this._priorityReverseScreenSpaceError = 0.0;
  this._foveatedFactor = 0.0;
  this._wasMinPriorityChild = false; // Needed for knowing when to continue a refinement chain. Gets reset in updateTile in traversal and gets set in updateAndPushChildren in traversal.

  this._loadTimestamp = new JulianDate();

  this._commandsLength = 0;

  this._color = undefined;
  this._colorDirty = false;

  this._request = undefined;
}

// This can be overridden for testing purposes
Cesium3DTile._deprecationWarning = deprecationWarning;

Object.defineProperties(Cesium3DTile.prototype, {
  /**
   * The tileset containing this tile.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {Cesium3DTileset}
   * @readonly
   */
  tileset: {
    get: function () {
      return this._tileset;
    },
  },

  /**
   * The tile's content.  This represents the actual tile's payload,
   * not the content's metadata in the tileset JSON file.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {Cesium3DTileContent}
   * @readonly
   */
  content: {
    get: function () {
      return this._content;
    },
  },

  /**
   * Get the tile's bounding volume.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {TileBoundingVolume}
   * @readonly
   * @private
   */
  boundingVolume: {
    get: function () {
      return this._boundingVolume;
    },
  },

  /**
   * Get the bounding volume of the tile's contents.  This defaults to the
   * tile's bounding volume when the content's bounding volume is
   * <code>undefined</code>.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {TileBoundingVolume}
   * @readonly
   * @private
   */
  contentBoundingVolume: {
    get: function () {
      return this._contentBoundingVolume ?? this._boundingVolume;
    },
  },

  /**
   * Get the bounding sphere derived from the tile's bounding volume.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {BoundingSphere}
   * @readonly
   */
  boundingSphere: {
    get: function () {
      return this._boundingVolume.boundingSphere;
    },
  },

  /**
   * Determines if the tile is visible within the current field of view
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  isVisible: {
    get: function () {
      return this._visible && this._inRequestVolume;
    },
  },

  /**
   * Returns the <code>extras</code> property in the tileset JSON for this tile, which contains application specific metadata.
   * Returns <code>undefined</code> if <code>extras</code> does not exist.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {object}
   * @readonly
   * @see {@link https://github.com/CesiumGS/3d-tiles/tree/main/specification#specifying-extensions-and-application-specific-extras|Extras in the 3D Tiles specification.}
   */
  extras: {
    get: function () {
      return this._header.extras;
    },
  },

  /**
   * Gets or sets the tile's highlight color.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {Color}
   *
   * @default {@link Color.WHITE}
   *
   * @private
   */
  color: {
    get: function () {
      if (!defined(this._color)) {
        this._color = new Color();
      }
      return Color.clone(this._color);
    },
    set: function (value) {
      this._color = Color.clone(value, this._color);
      this._colorDirty = true;
    },
  },

  /**
   * Determines if the tile has available content to render.  <code>true</code> if the tile's
   * content is ready or if it has expired content that renders while new content loads; otherwise,
   * <code>false</code>.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  contentAvailable: {
    get: function () {
      return (
        (this.contentReady && this.hasRenderableContent) ||
        (defined(this._expiredContent) && !this.contentFailed)
      );
    },
  },

  /**
   * Determines if the tile's content is ready. This is automatically <code>true</code> for
   * tile's with empty content.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  contentReady: {
    get: function () {
      return this._contentState === Cesium3DTileContentState.READY;
    },
  },

  /**
   * Determines if the tile's content has not be requested. <code>true</code> if tile's
   * content has not be requested; otherwise, <code>false</code>.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  contentUnloaded: {
    get: function () {
      return this._contentState === Cesium3DTileContentState.UNLOADED;
    },
  },

  /**
   * Determines if the tile has renderable content which is unloaded
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  hasUnloadedRenderableContent: {
    get: function () {
      return this.hasRenderableContent && this.contentUnloaded;
    },
  },

  /**
   * Determines if the tile's content is expired. <code>true</code> if tile's
   * content is expired; otherwise, <code>false</code>.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  contentExpired: {
    get: function () {
      return this._contentState === Cesium3DTileContentState.EXPIRED;
    },
  },

  /**
   * Determines if the tile's content failed to load.  <code>true</code> if the tile's
   * content failed to load; otherwise, <code>false</code>.
   *
   * @memberof Cesium3DTile.prototype
   *
   * @type {boolean}
   * @readonly
   *
   * @private
   */
  contentFailed: {
    get: function () {
      return this._contentState === Cesium3DTileContentState.FAILED;
    },
  },

  /**
   * Returns the number of draw commands used by this tile.
   *
   * @readonly
   *
   * @private
   */
  commandsLength: {
    get: function () {
      return this._commandsLength;
    },
  },
});

const scratchCartesian = new Cartesian3();

/**
 * @private
 * @param {Cesium3DTile} tile
 * @param {FrameState} frameState
 * @returns {boolean}
 */
function isPriorityDeferred(tile, frameState) {
  const { tileset, boundingSphere } = tile;
  const { radius, center } = boundingSphere;
  const { camera } = frameState;

  // If closest point on line is inside the sphere then set foveatedFactor to 0.
  // Otherwise, the dot product is with the line from camera to the point on the sphere that is closest to the line.
  const scaledCameraDirection = Cartesian3.multiplyByScalar(
    camera.directionWC,
    tile._centerZDepth,
    scratchCartesian,
  );
  const closestPointOnLine = Cartesian3.add(
    camera.positionWC,
    scaledCameraDirection,
    scratchCartesian,
  );
  // The distance from the camera's view direction to the tile.
  const toLine = Cartesian3.subtract(
    closestPointOnLine,
    center,
    scratchCartesian,
  );
  const distanceToCenterLine = Cartesian3.magnitude(toLine);
  const notTouchingSphere = distanceToCenterLine > radius;

  // If camera's direction vector is inside the bounding sphere then consider
  // this tile right along the line of sight and set _foveatedFactor to 0.
  // Otherwise,_foveatedFactor is one minus the dot product of the camera's direction
  // and the vector between the camera and the point on the bounding sphere closest to the view line.
  if (notTouchingSphere) {
    const toLineNormalized = Cartesian3.normalize(toLine, scratchCartesian);
    const scaledToLine = Cartesian3.multiplyByScalar(
      toLineNormalized,
      radius,
      scratchCartesian,
    );
    const closestOnSphere = Cartesian3.add(
      center,
      scaledToLine,
      scratchCartesian,
    );
    const toClosestOnSphere = Cartesian3.subtract(
      closestOnSphere,
      camera.positionWC,
      scratchCartesian,
    );
    const toClosestOnSphereNormalize = Cartesian3.normalize(
      toClosestOnSphere,
      scratchCartesian,
    );
    tile._foveatedFactor =
      1.0 -
      Math.abs(Cartesian3.dot(camera.directionWC, toClosestOnSphereNormalize));
  } else {
    tile._foveatedFactor = 0.0;
  }

  // Skip this feature if: non-skipLevelOfDetail and replace refine, if the foveated settings are turned off, if tile is progressive resolution and replace refine and skipLevelOfDetail (will help get rid of ancestor artifacts faster)
  // Or if the tile is a preload of any kind
  const replace = tile.refine === Cesium3DTileRefine.REPLACE;
  const skipLevelOfDetail = tileset.isSkippingLevelOfDetail;
  if (
    (replace && !skipLevelOfDetail) ||
    !tileset.foveatedScreenSpaceError ||
    tileset.foveatedConeSize === 1.0 ||
    (tile._priorityProgressiveResolution && replace && skipLevelOfDetail) ||
    tileset._pass === Cesium3DTilePass.PRELOAD_FLIGHT ||
    tileset._pass === Cesium3DTilePass.PRELOAD
  ) {
    return false;
  }

  const maximumFovatedFactor = 1.0 - Math.cos(camera.frustum.fov * 0.5); // 0.14 for fov = 60. NOTE very hard to defer vertically foveated tiles since max is based on fovy (which is fov). Lowering the 0.5 to a smaller fraction of the screen height will start to defer vertically foveated tiles.
  const foveatedConeFactor = tileset.foveatedConeSize * maximumFovatedFactor;

  // If it's inside the user-defined view cone, then it should not be deferred.
  if (tile._foveatedFactor <= foveatedConeFactor) {
    return false;
  }

  // Relax SSE based on how big the angle is between the tile and the edge of the foveated cone.
  const range = maximumFovatedFactor - foveatedConeFactor;
  const normalizedFoveatedFactor = CesiumMath.clamp(
    (tile._foveatedFactor - foveatedConeFactor) / range,
    0.0,
    1.0,
  );
  const sseRelaxation = tileset.foveatedInterpolationCallback(
    tileset.foveatedMinimumScreenSpaceErrorRelaxation,
    tileset.memoryAdjustedScreenSpaceError,
    normalizedFoveatedFactor,
  );
  const sse =
    tile._screenSpaceError === 0.0 && defined(tile.parent)
      ? tile.parent._screenSpaceError * 0.5
      : tile._screenSpaceError;

  return tileset.memoryAdjustedScreenSpaceError - sseRelaxation <= sse;
}

const scratchJulianDate = new JulianDate();

/**
 * Get the tile's screen space error.
 *
 * @private
 * @param {FrameState} frameState
 * @param {boolean} useParentGeometricError
 * @param {number} progressiveResolutionHeightFraction
 */
Cesium3DTile.prototype.getScreenSpaceError = function (
  frameState,
  useParentGeometricError,
  progressiveResolutionHeightFraction,
) {
  const tileset = this._tileset;
  const heightFraction = progressiveResolutionHeightFraction ?? 1.0;
  const parentGeometricError = defined(this.parent)
    ? this.parent.geometricError
    : tileset._scaledGeometricError;
  const geometricError = useParentGeometricError
    ? parentGeometricError
    : this.geometricError;
  if (geometricError === 0.0) {
    // Leaf tiles do not have any error so save the computation
    return 0.0;
  }
  const { camera, context } = frameState;
  let frustum = camera.frustum;
  const width = context.drawingBufferWidth;
  const height = context.drawingBufferHeight * heightFraction;
  let error;
  if (
    frameState.mode === SceneMode.SCENE2D ||
    frustum instanceof OrthographicFrustum
  ) {
    const offCenterFrustum = frustum.offCenterFrustum;
    if (defined(offCenterFrustum)) {
      frustum = offCenterFrustum;
    }
    const pixelSize =
      Math.max(frustum.top - frustum.bottom, frustum.right - frustum.left) /
      Math.max(width, height);
    error = geometricError / pixelSize;
  } else {
    // Avoid divide by zero when viewer is inside the tile
    const distance = Math.max(this._distanceToCamera, CesiumMath.EPSILON7);
    const sseDenominator = frustum.sseDenominator;
    error = (geometricError * height) / (distance * sseDenominator);
    if (tileset.dynamicScreenSpaceError) {
      const density = tileset._dynamicScreenSpaceErrorComputedDensity;
      const factor = tileset.dynamicScreenSpaceErrorFactor;
      const dynamicError = CesiumMath.fog(distance, density) * factor;
      error -= dynamicError;
    }
  }

  error /= frameState.pixelRatio;

  return error;
};

/**
 * @private
 * @param {Cesium3DTileset} tileset
 * @param {Cesium3DTile} tile
 * @returns {boolean}
 */
function isPriorityProgressiveResolution(tileset, tile) {
  if (
    tileset.progressiveResolutionHeightFraction <= 0.0 ||
    tileset.progressiveResolutionHeightFraction > 0.5
  ) {
    return false;
  }

  const maximumScreenSpaceError = tileset.memoryAdjustedScreenSpaceError;
  let isProgressiveResolutionTile =
    tile._screenSpaceErrorProgressiveResolution > maximumScreenSpaceError; // Mark non-SSE leaves
  tile._priorityProgressiveResolutionScreenSpaceErrorLeaf = false; // Needed for skipLOD
  const parent = tile.parent;
  const tilePasses =
    tile._screenSpaceErrorProgressiveResolution <= maximumScreenSpaceError;
  const parentFails =
    defined(parent) &&
    parent._screenSpaceErrorProgressiveResolution > maximumScreenSpaceError;
  if (tilePasses && parentFails) {
    // A progressive resolution SSE leaf, promote its priority as well
    tile._priorityProgressiveResolutionScreenSpaceErrorLeaf = true;
    isProgressiveResolutionTile = true;
  }
  return isProgressiveResolutionTile;
}

/**
 * @private
 * @param {Cesium3DTileset} tileset
 * @param {Cesium3DTile} tile
 * @returns {number}
 */
function getPriorityReverseScreenSpaceError(tileset, tile) {
  const parent = tile.parent;
  const useParentScreenSpaceError =
    defined(parent) &&
    (!tileset.isSkippingLevelOfDetail ||
      tile._screenSpaceError === 0.0 ||
      parent.hasTilesetContent ||
      parent.hasImplicitContent);
  const screenSpaceError = useParentScreenSpaceError
    ? parent._screenSpaceError
    : tile._screenSpaceError;
  return tileset.root._screenSpaceError - screenSpaceError;
}

/**
 * Update the tile's visibility.
 *
 * @private
 * @param {FrameState} frameState
 */
Cesium3DTile.prototype.updateVisibility = function (frameState) {
  const { parent, tileset } = this;
  if (this._updatedVisibilityFrame === tileset._updatedVisibilityFrame) {
    // The tile has already been updated for this frame
    return;
  }

  const parentTransform = defined(parent)
    ? parent.computedTransform
    : tileset.modelMatrix;
  const parentVisibilityPlaneMask = defined(parent)
    ? parent._visibilityPlaneMask
    : CullingVolume.MASK_INDETERMINATE;
  this.updateTransform(parentTransform, frameState);
  this._distanceToCamera = this.distanceToTile(frameState);
  this._centerZDepth = this.distanceToTileCenter(frameState);
  this._screenSpaceError = this.getScreenSpaceError(frameState, false);
  this._screenSpaceErrorProgressiveResolution = this.getScreenSpaceError(
    frameState,
    false,
    tileset.progressiveResolutionHeightFraction,
  );
  this._visibilityPlaneMask = this.visibility(
    frameState,
    parentVisibilityPlaneMask,
  ); // Use parent's plane mask to speed up visibility test
  this._visible = this._visibilityPlaneMask !== CullingVolume.MASK_OUTSIDE;
  this._inRequestVolume = this.insideViewerRequestVolume(frameState);
  this._priorityReverseScreenSpaceError = getPriorityReverseScreenSpaceError(
    tileset,
    this,
  );
  this._priorityProgressiveResolution = isPriorityProgressiveResolution(
    tileset,
    this,
  );
  this.priorityDeferred = isPriorityDeferred(this, frameState);

  this._updatedVisibilityFrame = tileset._updatedVisibilityFrame;
};

/**
 * Update whether the tile has expired.
 *
 * @private
 */
Cesium3DTile.prototype.updateExpiration = function () {
  if (
    defined(this.expireDate) &&
    this.contentReady &&
    !this.hasEmptyContent &&
    !this.hasMultipleContents
  ) {
    const now = JulianDate.now(scratchJulianDate);
    if (JulianDate.lessThan(this.expireDate, now)) {
      this._contentState = Cesium3DTileContentState.EXPIRED;
      this._expiredContent = this._content;
    }
  }
};

/**
 * @private
 * @param {Cesium3DTile} tile
 */
function updateExpireDate(tile) {
  if (!defined(tile.expireDuration)) {
    return;
  }
  const expireDurationDate = JulianDate.now(scratchJulianDate);
  JulianDate.addSeconds(
    expireDurationDate,
    tile.expireDuration,
    expireDurationDate,
  );

  if (defined(tile.expireDate)) {
    if (JulianDate.lessThan(tile.expireDate, expireDurationDate)) {
      JulianDate.clone(expireDurationDate, tile.expireDate);
    }
  } else {
    tile.expireDate = JulianDate.clone(expireDurationDate);
  }
}

/**
 * @private
 * @param {Cesium3DTile} tile
 * @returns {Function}
 */
function createPriorityFunction(tile) {
  return function () {
    return tile._priority;
  };
}

/**
 * Requests the tile's content.
 * <p>
 * The request may not be made if the Cesium Request Scheduler can't prioritize it.
 * </p>
 *
 * @return {Promise<Cesium3DTileContent>|undefined} A promise that resolves when the request completes, or undefined if there is no request needed, or the request cannot be scheduled.
 * @private
 */
Cesium3DTile.prototype.requestContent = function () {
  // empty contents don't require any HTTP requests
  if (this.hasEmptyContent) {
    return;
  }

  if (this.hasMultipleContents) {
    return requestMultipleContents(this);
  }

  return requestSingleContent(this);
};

/**
 * Multiple {@link Cesium3DTileContent}s are allowed within a single tile either through
 * the tile JSON (3D Tiles 1.1) or the <code>3DTILES_multiple_contents</code> extension.
 * Due to differences in request scheduling, this is handled separately.
 * <p>
 * This implementation of multiple contents does not
 * support tile expiry like requestSingleContent does. If this changes,
 * note that the resource.setQueryParameters() details must go inside {@link Multiple3DTileContent} since that is per-request.
 * </p>
 *
 * @private
 * @param {Cesium3DTile} tile
 * @returns {Promise<Cesium3DTileContent>|Promise<undefined>|undefined} A promise that resolves to the tile content once loaded, or a promise that resolves to undefined if the request was cancelled mid-flight, or undefined if the request cannot be scheduled this frame
 */
function requestMultipleContents(tile) {
  let multipleContents = tile._content;
  const tileset = tile._tileset;

  if (!defined(multipleContents)) {
    // Create the content object immediately, it will handle scheduling
    // requests for inner contents.
    const contentsJson = hasExtension(tile._header, "3DTILES_multiple_contents")
      ? tile._header.extensions["3DTILES_multiple_contents"]
      : tile._header;

    multipleContents = new Multiple3DTileContent(
      tileset,
      tile,
      tile._contentResource.clone(),
      contentsJson,
    );
    tile._content = multipleContents;
  }

  const promise = multipleContents.requestInnerContents();

  if (!defined(promise)) {
    // Request could not all be scheduled this frame
    return;
  }

  tile._contentState = Cesium3DTileContentState.LOADING;
  return promise
    .then((content) => {
      if (tile.isDestroyed()) {
        // Tile is unloaded before the content can process
        return;
      }

      // Tile was canceled, try again later
      if (!defined(content)) {
        return;
      }

      tile._contentState = Cesium3DTileContentState.PROCESSING;
      return multipleContents;
    })
    .catch((error) => {
      if (tile.isDestroyed()) {
        // Tile is unloaded before the content can process
        return;
      }

      tile._contentState = Cesium3DTileContentState.FAILED;
      throw error;
    });
}

async function processArrayBuffer(
  tile,
  tileset,
  request,
  expired,
  requestPromise,
) {
  const previousState = tile._contentState;
  tile._contentState = Cesium3DTileContentState.LOADING;
  ++tileset.statistics.numberOfPendingRequests;

  let arrayBuffer;
  try {
    arrayBuffer = await requestPromise;
  } catch (error) {
    --tileset.statistics.numberOfPendingRequests;
    if (tile.isDestroyed()) {
      // Tile is unloaded before the content can process
      return;
    }

    if (request.cancelled || request.state === RequestState.CANCELLED) {
      // Cancelled due to low priority - try again later.
      tile._contentState = previousState;
      ++tileset.statistics.numberOfAttemptedRequests;
      return;
    }

    tile._contentState = Cesium3DTileContentState.FAILED;
    throw error;
  }

  if (tile.isDestroyed()) {
    --tileset.statistics.numberOfPendingRequests;
    // Tile is unloaded before the content can process
    return;
  }

  if (request.cancelled || request.state === RequestState.CANCELLED) {
    // Cancelled due to low priority - try again later.
    tile._contentState = previousState;
    --tileset.statistics.numberOfPendingRequests;
    ++tileset.statistics.numberOfAttemptedRequests;
    return;
  }

  try {
    const content = await makeContent(tile, arrayBuffer);
    --tileset.statistics.numberOfPendingRequests;

    if (tile.isDestroyed()) {
      // Tile is unloaded before the content can process
      return;
    }

    if (expired) {
      tile.expireDate = undefined;
    }

    tile._content = content;
    tile._contentState = Cesium3DTileContentState.PROCESSING;

    return content;
  } catch (error) {
    --tileset.statistics.numberOfPendingRequests;
    if (tile.isDestroyed()) {
      // Tile is unloaded before the content can process
      return;
    }

    tile._contentState = Cesium3DTileContentState.FAILED;
    throw error;
  }
}

/**
 * @private
 * @param {Cesium3DTile} tile
 * @returns {Promise<Cesium3DTileContent>|Promise<undefined>|undefined} A promise that resolves to the tile content once loaded; a promise that resolves to undefined if the tile was destroyed before processing can happen or the request was cancelled mid-flight; or undefined if the request cannot be scheduled this frame.
 */
function requestSingleContent(tile) {
  // it is important to clone here. The fetchArrayBuffer() below uses
  // throttling, but other uses of the resources do not.
  const resource = tile._contentResource.clone();
  const expired = tile.contentExpired;
  if (expired) {
    // Append a query parameter of the tile expiration date to prevent caching
    resource.setQueryParameters({
      expired: tile.expireDate.toString(),
    });
  }

  const request = new Request({
    throttle: true,
    throttleByServer: true,
    type: RequestType.TILES3D,
    priorityFunction: createPriorityFunction(tile),
    serverKey: tile._serverKey,
  });

  tile._request = request;
  resource.request = request;
  const tileset = tile._tileset;
  const promise = resource.fetchArrayBuffer();
  if (!defined(promise)) {
    ++tileset.statistics.numberOfAttemptedRequests;
    return;
  }

  return processArrayBuffer(tile, tileset, request, expired, promise);
}

/**
 * Given a downloaded content payload, construct a {@link Cesium3DTileContent}.
 * <p>
 * This is only used for single contents.
 * </p>
 *
 * @param {Cesium3DTile} tile The tile
 * @param {ArrayBuffer} arrayBuffer The downloaded payload containing data for the content
 * @return {Promise<Cesium3DTileContent>} A content object
 * @private
 */
async function makeContent(tile, arrayBuffer) {
  const preprocessed = preprocess3DTileContent(arrayBuffer);

  // Vector and Geometry tile rendering do not support the skip LOD optimization.
  const tileset = tile._tileset;
  tileset._disableSkipLevelOfDetail =
    tileset._disableSkipLevelOfDetail ||
    preprocessed.contentType === Cesium3DTileContentType.GEOMETRY ||
    preprocessed.contentType === Cesium3DTileContentType.VECTOR;

  if (
    preprocessed.contentType === Cesium3DTileContentType.IMPLICIT_SUBTREE ||
    preprocessed.contentType === Cesium3DTileContentType.IMPLICIT_SUBTREE_JSON
  ) {
    tile.hasImplicitContent = true;
    tile.hasRenderableContent = false;
  }

  if (preprocessed.contentType === Cesium3DTileContentType.EXTERNAL_TILESET) {
    tile.hasTilesetContent = true;
    tile.hasRenderableContent = false;
  }

  let content;
  const contentFactory = Cesium3DTileContentFactory[preprocessed.contentType];
  if (tile.isDestroyed()) {
    return;
  }

  if (defined(preprocessed.binaryPayload)) {
    content = await Promise.resolve(
      contentFactory(
        tileset,
        tile,
        tile._contentResource,
        preprocessed.binaryPayload.buffer,
        0,
      ),
    );
  } else {
    // JSON formats
    content = await Promise.resolve(
      contentFactory(
        tileset,
        tile,
        tile._contentResource,
        preprocessed.jsonPayload,
      ),
    );
  }

  const contentHeader = tile._contentHeader;

  if (tile.hasImplicitContentMetadata) {
    const subtree = tile.implicitSubtree;
    const coordinates = tile.implicitCoordinates;
    content.metadata = subtree.getContentMetadataView(coordinates, 0);
  } else if (!tile.hasImplicitContent) {
    content.metadata = findContentMetadata(tileset, contentHeader);
  }

  const groupMetadata = findGroupMetadata(tileset, contentHeader);
  if (defined(groupMetadata)) {
    content.group = new Cesium3DContentGroup({
      metadata: groupMetadata,
    });
  }

  return content;
}

/**
 * Cancel requests for the tile's contents. This is called when the tile
 * goes out of view.
 *
 * @private
 */
Cesium3DTile.prototype.cancelRequests = function () {
  if (this.hasMultipleContents) {
    this._content.cancelRequests();
  } else {
    this._request.cancel();
  }
};

/**
 * Unloads the tile's content.
 *
 * @private
 */
Cesium3DTile.prototype.unloadContent = function () {
  if (!this.hasRenderableContent) {
    return;
  }

  this._content = this._content && this._content.destroy();
  this._contentState = Cesium3DTileContentState.UNLOADED;

  this.lastStyleTime = 0.0;
  this.clippingPlanesDirty = this._clippingPlanesState === 0;
  this._clippingPlanesState = 0;
  this.clippingPolygonsDirty = this._clippingPolygonsState === 0;
  this._clippingPolygonsState = 0;

  this._debugColorizeTiles = false;

  this._debugBoundingVolume =
    this._debugBoundingVolume && this._debugBoundingVolume.destroy();
  this._debugContentBoundingVolume =
    this._debugContentBoundingVolume &&
    this._debugContentBoundingVolume.destroy();
  this._debugViewerRequestVolume =
    this._debugViewerRequestVolume && this._debugViewerRequestVolume.destroy();
};

const scratchProjectedBoundingSphere = new BoundingSphere();

/**
 * @private
 * @param {Cesium3DTile} tile
 * @param {FrameState} frameState
 * @returns {TileBoundingVolume}
 */
function getBoundingVolume(tile, frameState) {
  if (
    frameState.mode !== SceneMode.SCENE3D &&
    !defined(tile._boundingVolume2D)
  ) {
    const boundingSphere = tile._boundingVolume.boundingSphere;
    const sphere = BoundingSphere.projectTo2D(
      boundingSphere,
      frameState.mapProjection,
      scratchProjectedBoundingSphere,
    );
    tile._boundingVolume2D = new TileBoundingSphere(
      sphere.center,
      sphere.radius,
    );
  }

  return frameState.mode !== SceneMode.SCENE3D
    ? tile._boundingVolume2D
    : tile._boundingVolume;
}

/**
 * @private
 * @param {Cesium3DTile} tile
 * @param {FrameState} frameState
 * @returns {TileBoundingVolume}
 */
function getContentBoundingVolume(tile, frameState) {
  if (
    frameState.mode !== SceneMode.SCENE3D &&
    !defined(tile._contentBoundingVolume2D)
  ) {
    const boundingSphere = tile._contentBoundingVolume.boundingSphere;
    const sphere = BoundingSphere.projectTo2D(
      boundingSphere,
      frameState.mapProjection,
      scratchProjectedBoundingSphere,
    );
    tile._contentBoundingVolume2D = new TileBoundingSphere(
      sphere.center,
      sphere.radius,
    );
  }
  return frameState.mode !== SceneMode.SCENE3D
    ? tile._contentBoundingVolume2D
    : tile._contentBoundingVolume;
}

/**
 * Determines whether the tile's bounding volume intersects the culling volume.
 *
 * @param {FrameState} frameState The frame state.
 * @param {number} parentVisibilityPlaneMask The parent's plane mask to speed up the visibility check.
 * @returns {number} A plane mask as described above in {@link CullingVolume#computeVisibilityWithPlaneMask}.
 *
 * @private
 */
Cesium3DTile.prototype.visibility = function (
  frameState,
  parentVisibilityPlaneMask,
) {
  const cullingVolume = frameState.cullingVolume;
  const boundingVolume = getBoundingVolume(this, frameState);

  const tileset = this._tileset;
  const clippingPlanes = tileset.clippingPlanes;
  if (defined(clippingPlanes) && clippingPlanes.enabled) {
    const intersection = clippingPlanes.computeIntersectionWithBoundingVolume(
      boundingVolume,
      tileset.clippingPlanesOriginMatrix,
    );
    this._isClipped = intersection !== Intersect.INSIDE;
    if (intersection === Intersect.OUTSIDE) {
      return CullingVolume.MASK_OUTSIDE;
    }
  }

  const clippingPolygons = tileset.clippingPolygons;
  if (defined(clippingPolygons) && clippingPolygons.enabled) {
    const intersection =
      clippingPolygons.computeIntersectionWithBoundingVolume(boundingVolume);

    this._isClippedByPolygon = intersection !== Intersect.OUTSIDE;
    // Polygon clipping intersections are determined by outer rectangles, therefore we cannot
    // preemptively determine if a tile is completely clipped or not here.
  }

  return cullingVolume.computeVisibilityWithPlaneMask(
    boundingVolume,
    parentVisibilityPlaneMask,
  );
};

/**
 * Assuming the tile's bounding volume intersects the culling volume, determines
 * whether the tile's content's bounding volume intersects the culling volume.
 *
 * @param {FrameState} frameState The frame state.
 * @returns {Intersect} The result of the intersection: the tile's content is completely outside, completely inside, or intersecting the culling volume.
 *
 * @private
 */
Cesium3DTile.prototype.contentVisibility = function (frameState) {
  // Assumes the tile's bounding volume intersects the culling volume already, so
  // just return Intersect.INSIDE if there is no content bounding volume.
  if (!defined(this._contentBoundingVolume)) {
    return Intersect.INSIDE;
  }

  if (this._visibilityPlaneMask === CullingVolume.MASK_INSIDE) {
    // The tile's bounding volume is completely inside the culling volume so
    // the content bounding volume must also be inside.
    return Intersect.INSIDE;
  }

  // PERFORMANCE_IDEA: is it possible to burn less CPU on this test since we know the
  // tile's (not the content's) bounding volume intersects the culling volume?
  const cullingVolume = frameState.cullingVolume;
  const boundingVolume = getContentBoundingVolume(this, frameState);

  const tileset = this._tileset;
  const clippingPlanes = tileset.clippingPlanes;
  if (defined(clippingPlanes) && clippingPlanes.enabled) {
    const intersection = clippingPlanes.computeIntersectionWithBoundingVolume(
      boundingVolume,
      tileset.clippingPlanesOriginMatrix,
    );
    this._isClipped = intersection !== Intersect.INSIDE;
    if (intersection === Intersect.OUTSIDE) {
      return Intersect.OUTSIDE;
    }
  }

  const clippingPolygons = tileset.clippingPolygons;
  if (defined(clippingPolygons) && clippingPolygons.enabled) {
    const intersection =
      clippingPolygons.computeIntersectionWithBoundingVolume(boundingVolume);
    this._isClippedByPolygon = intersection !== Intersect.OUTSIDE;
    if (intersection === Intersect.INSIDE) {
      return Intersect.OUTSIDE;
    }
  }

  return cullingVolume.computeVisibility(boundingVolume);
};

/**
 * Computes the (potentially approximate) distance from the closest point of the tile's bounding volume to the camera.
 *
 * @param {FrameState} frameState The frame state.
 * @returns {number} The distance, in meters, or zero if the camera is inside the bounding volume.
 *
 * @private
 */
Cesium3DTile.prototype.distanceToTile = function (frameState) {
  const boundingVolume = getBoundingVolume(this, frameState);
  return boundingVolume.distanceToCamera(frameState);
};

const scratchToTileCenter = new Cartesian3();

/**
 * Computes the distance from the center of the tile's bounding volume to the camera's plane defined by its position and view direction.
 *
 * @param {FrameState} frameState The frame state.
 * @returns {number} The distance, in meters.
 *
 * @private
 */
Cesium3DTile.prototype.distanceToTileCenter = function (frameState) {
  const tileBoundingVolume = getBoundingVolume(this, frameState);
  const boundingVolume = tileBoundingVolume.boundingVolume; // Gets the underlying OrientedBoundingBox or BoundingSphere
  const toCenter = Cartesian3.subtract(
    boundingVolume.center,
    frameState.camera.posi