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Cesium3DTilesetBaseTraversal.js
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Cesium3DTilesetBaseTraversal.js
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import defined from "../Core/defined.js";
import ManagedArray from "../Core/ManagedArray.js";
import Cesium3DTileRefine from "./Cesium3DTileRefine.js";
import Cesium3DTilesetTraversal from "./Cesium3DTilesetTraversal.js";
/**
* Depth-first traversal that traverses all visible tiles and marks tiles for selection.
* A tile does not refine until all children are loaded.
* This is the traditional replacement refinement approach and is called the base traversal.
*
* @alias Cesium3DTilesetBaseTraversal
* @constructor
*
* @private
*/
function Cesium3DTilesetBaseTraversal() {}
const traversal = {
stack: new ManagedArray(),
stackMaximumLength: 0,
};
const emptyTraversal = {
stack: new ManagedArray(),
stackMaximumLength: 0,
};
/**
* Traverses a {@link Cesium3DTileset} to determine which tiles to load and render.
*
* @private
* @param {Cesium3DTileset} tileset
* @param {FrameState} frameState
*/
Cesium3DTilesetBaseTraversal.selectTiles = function (tileset, frameState) {
tileset._requestedTiles.length = 0;
if (tileset.debugFreezeFrame) {
return;
}
tileset._selectedTiles.length = 0;
tileset._selectedTilesToStyle.length = 0;
tileset._emptyTiles.length = 0;
tileset.hasMixedContent = false;
const root = tileset.root;
Cesium3DTilesetTraversal.updateTile(root, frameState);
if (!root.isVisible) {
return;
}
if (
root.getScreenSpaceError(frameState, true) <=
tileset.memoryAdjustedScreenSpaceError
) {
return;
}
executeTraversal(root, frameState);
traversal.stack.trim(traversal.stackMaximumLength);
emptyTraversal.stack.trim(emptyTraversal.stackMaximumLength);
// Update the priority for any requests found during traversal
// Update after traversal so that min and max values can be used to normalize priority values
const requestedTiles = tileset._requestedTiles;
for (let i = 0; i < requestedTiles.length; ++i) {
requestedTiles[i].updatePriority();
}
};
/**
* Mark a tile as selected if it has content available.
*
* @private
* @param {Cesium3DTile} tile
* @param {FrameState} frameState
*/
function selectDesiredTile(tile, frameState) {
if (tile.contentAvailable) {
Cesium3DTilesetTraversal.selectTile(tile, frameState);
}
}
/**
* @private
* @param {Cesium3DTile} tile
* @param {ManagedArray} stack
* @param {FrameState} frameState
* @returns {boolean}
*/
function updateAndPushChildren(tile, stack, frameState) {
const replace = tile.refine === Cesium3DTileRefine.REPLACE;
const { tileset, children } = tile;
const { updateTile, loadTile, touchTile } = Cesium3DTilesetTraversal;
for (let i = 0; i < children.length; ++i) {
updateTile(children[i], frameState);
}
// Sort by distance to take advantage of early Z and reduce artifacts for skipLevelOfDetail
children.sort(Cesium3DTilesetTraversal.sortChildrenByDistanceToCamera);
// For traditional replacement refinement only refine if all children are loaded.
// Empty tiles are exempt since it looks better if children stream in as they are loaded to fill the empty space.
const checkRefines = replace && tile.hasRenderableContent;
let refines = true;
let anyChildrenVisible = false;
// Determining min child
let minIndex = -1;
let minimumPriority = Number.MAX_VALUE;
for (let i = 0; i < children.length; ++i) {
const child = children[i];
if (child.isVisible) {
stack.push(child);
if (child._foveatedFactor < minimumPriority) {
minIndex = i;
minimumPriority = child._foveatedFactor;
}
anyChildrenVisible = true;
} else if (checkRefines || tileset.loadSiblings) {
// Keep non-visible children loaded since they are still needed before the parent can refine.
// Or loadSiblings is true so always load tiles regardless of visibility.
if (child._foveatedFactor < minimumPriority) {
minIndex = i;
minimumPriority = child._foveatedFactor;
}
loadTile(child, frameState);
touchTile(child, frameState);
}
if (checkRefines) {
let childRefines;
if (!child._inRequestVolume) {
childRefines = false;
} else if (!child.hasRenderableContent) {
childRefines = executeEmptyTraversal(child, frameState);
} else {
childRefines = child.contentAvailable;
}
refines = refines && childRefines;
}
}
if (!anyChildrenVisible) {
refines = false;
}
if (minIndex !== -1 && replace) {
// An ancestor will hold the _foveatedFactor and _distanceToCamera for descendants between itself and its highest priority descendant. Siblings of a min children along the way use this ancestor as their priority holder as well.
// Priority of all tiles that refer to the _foveatedFactor and _distanceToCamera stored in the common ancestor will be differentiated based on their _depth.
const minPriorityChild = children[minIndex];
minPriorityChild._wasMinPriorityChild = true;
const priorityHolder =
(tile._wasMinPriorityChild || tile === tileset.root) &&
minimumPriority <= tile._priorityHolder._foveatedFactor
? tile._priorityHolder
: tile; // This is where priority dependency chains are wired up or started anew.
priorityHolder._foveatedFactor = Math.min(
minPriorityChild._foveatedFactor,
priorityHolder._foveatedFactor
);
priorityHolder._distanceToCamera = Math.min(
minPriorityChild._distanceToCamera,
priorityHolder._distanceToCamera
);
for (let i = 0; i < children.length; ++i) {
children[i]._priorityHolder = priorityHolder;
}
}
return refines;
}
/**
* Depth-first traversal that traverses all visible tiles and marks tiles for selection.
* A tile does not refine until all children are loaded.
* This is the traditional replacement refinement approach and is called the base traversal.
*
* @private
* @param {Cesium3DTile} root
* @param {FrameState} frameState
*/
function executeTraversal(root, frameState) {
const { tileset } = root;
const {
canTraverse,
loadTile,
visitTile,
touchTile,
} = Cesium3DTilesetTraversal;
const stack = traversal.stack;
stack.push(root);
while (stack.length > 0) {
traversal.stackMaximumLength = Math.max(
traversal.stackMaximumLength,
stack.length
);
const tile = stack.pop();
const parent = tile.parent;
const parentRefines = !defined(parent) || parent._refines;
tile._refines = canTraverse(tile)
? updateAndPushChildren(tile, stack, frameState) && parentRefines
: false;
const stoppedRefining = !tile._refines && parentRefines;
if (!tile.hasRenderableContent) {
// Add empty tile just to show its debug bounding volume
// If the tile has tileset content load the external tileset
tileset._emptyTiles.push(tile);
loadTile(tile, frameState);
if (stoppedRefining) {
selectDesiredTile(tile, frameState);
}
} else if (tile.refine === Cesium3DTileRefine.ADD) {
// Additive tiles are always loaded and selected
selectDesiredTile(tile, frameState);
loadTile(tile, frameState);
} else if (tile.refine === Cesium3DTileRefine.REPLACE) {
loadTile(tile, frameState);
if (stoppedRefining) {
selectDesiredTile(tile, frameState);
}
}
visitTile(tile, frameState);
touchTile(tile, frameState);
}
}
/**
* Depth-first traversal that checks if all nearest descendants with content are loaded.
* Ignores visibility.
*
* @private
* @param {Cesium3DTile} root
* @param {FrameState} frameState
* @returns {boolean}
*/
function executeEmptyTraversal(root, frameState) {
const {
canTraverse,
updateTile,
loadTile,
touchTile,
} = Cesium3DTilesetTraversal;
let allDescendantsLoaded = true;
const stack = emptyTraversal.stack;
stack.push(root);
while (stack.length > 0) {
emptyTraversal.stackMaximumLength = Math.max(
emptyTraversal.stackMaximumLength,
stack.length
);
const tile = stack.pop();
const children = tile.children;
const childrenLength = children.length;
// Only traverse if the tile is empty - traversal stops at descendants with content
const traverse = !tile.hasRenderableContent && canTraverse(tile);
// Traversal stops but the tile does not have content yet
// There will be holes if the parent tries to refine to its children, so don't refine
if (!traverse && !tile.contentAvailable) {
allDescendantsLoaded = false;
}
updateTile(tile, frameState);
if (!tile.isVisible) {
// Load tiles that aren't visible since they are still needed for the parent to refine
loadTile(tile, frameState);
touchTile(tile, frameState);
}
if (traverse) {
for (let i = 0; i < childrenLength; ++i) {
const child = children[i];
stack.push(child);
}
}
}
return root.hasEmptyContent || allDescendantsLoaded;
}
export default Cesium3DTilesetBaseTraversal;