CesiumGS · pjcozzi · Nov 8, 2018 · Sep 18, 2018 · Sep 19, 2018 · Sep 21, 2018
diff --git a/Apps/Sandcastle/gallery/Sample Height from 3D Tiles.html b/Apps/Sandcastle/gallery/Sample Height from 3D Tiles.html
@@ -0,0 +1,106 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
+    <meta name="description" content="Sample the most detailed heights of a 3D Tileset.">
+    <meta name="cesium-sandcastle-labels" content="Showcases, 3D Tiles">
+    <title>Cesium Demo</title>
+    <script type="text/javascript" src="../Sandcastle-header.js"></script>
+    <script type="text/javascript" src="../../../ThirdParty/requirejs-2.1.20/require.js"></script>
+    <script type="text/javascript">
+        if(typeof require === 'function') {
+            require.config({
+                baseUrl : '../../../Source',
+                waitSeconds : 120
+            });
+        }
+    </script>
+</head>
+<body class="sandcastle-loading" data-sandcastle-bucket="bucket-requirejs.html">
+<style>
+    @import url(../templates/bucket.css);
+</style>
+<div id="cesiumContainer" class="fullSize"></div>
+<div id="loadingOverlay"><h1>Loading...</h1></div>
+<div id="toolbar"></div>
+<script id="cesium_sandcastle_script">
+function startup(Cesium) {
+    'use strict';
+//Sandcastle_Begin
+var viewer = new Cesium.Viewer('cesiumContainer', {
+    terrainProvider : Cesium.createWorldTerrain()
+});
+var scene = viewer.scene;
+
+var tileset = scene.primitives.add(
+    new Cesium.Cesium3DTileset({
+        url: Cesium.IonResource.fromAssetId(6074)
+    })
+);
+
+scene.camera.setView({
+    destination: new Cesium.Cartesian3(1216411.0748779264, -4736313.10747583, 4081359.5125561724),
+    orientation: new Cesium.HeadingPitchRoll(4.239925103568368, -0.4911293834802475, 6.279849292088564),
+    endTransform : Cesium.Matrix4.IDENTITY
+});
+
+Sandcastle.addToolbarButton('Sample heights', function() {
+    sampleHeights();
+});
+
+function sampleHeights() {
+    if (!scene.clampToHeightSupported) {
+        console.log('This browser does not support clampToHeightMostDetailed.');
+    }
+
+    viewer.entities.removeAll();
+
+    var cartesian1 = new Cesium.Cartesian3(1216390.063324395, -4736314.814479433, 4081341.9787972216);
+    var cartesian2 = new Cesium.Cartesian3(1216329.5413318684, -4736272.029009798, 4081407.9342479417);
+
+    var count = 30;
+    var cartesians = new Array(count);
+    for (var i = 0; i < count; ++i) {
+        var offset = i / (count - 1);
+        cartesians[i] = Cesium.Cartesian3.lerp(cartesian1, cartesian2, offset, new Cesium.Cartesian3());
+    }
+
+    scene.clampToHeightMostDetailed(cartesians).then(function(clampedCartesians) {
+        for (var i = 0; i < count; ++i) {
+            viewer.entities.add({
+                position: clampedCartesians[i],
+                ellipsoid : {
+                    radii : new Cesium.Cartesian3(0.2, 0.2, 0.2),
+                    material : Cesium.Color.RED
+                }
+            });
+        }
+
+        viewer.entities.add({
+            polyline : {
+                positions : clampedCartesians,
+                followSurface : false,
+                width : 2,
+                material : new Cesium.PolylineOutlineMaterialProperty({
+                    color : Cesium.Color.YELLOW
+                }),
+                depthFailMaterial : new Cesium.PolylineOutlineMaterialProperty({
+                    color : Cesium.Color.YELLOW
+                })
+            }
+        });
+    });
+}
+//Sandcastle_End
+    Sandcastle.finishedLoading();
+}
+if (typeof Cesium !== 'undefined') {
+    startup(Cesium);
+} else if (typeof require === 'function') {
+    require(['Cesium'], startup);
+}
+</script>
+</body>
+</html>
diff --git a/Apps/Sandcastle/gallery/Sample Height from 3D Tiles.jpg b/Apps/Sandcastle/gallery/Sample Height from 3D Tiles.jpg
diff --git a/CHANGES.md b/CHANGES.md
@@ -4,6 +4,9 @@ Change Log
 ### 1.52 - 2018-12-03
 
 ##### Additions :tada:
+* Added functions to get the most detailed height of 3D Tiles on-screen or off-screen. [#7115](https://github.com/AnalyticalGraphicsInc/cesium/pull/7115)
+    * Added `Scene.sampleHeightMostDetailed`, an asynchronous version of `Scene.sampleHeight` that uses the maximum level of detail for 3D Tiles.
+    * Added `Scene.clampToHeightMostDetailed`, an asynchronous version of `Scene.clampToHeight` that uses the maximum level of detail for 3D Tiles.
 * Added `Scene.invertClassificationSupported` for checking if invert classification is supported.
 * Added `computeLineSegmentLineSegmentIntersection` to `Intersections2D`. [#7228](https://github.com/AnalyticalGraphicsInc/Cesium/pull/7228)
 

diff --git a/Source/Scene/Cesium3DTileset.js b/Source/Scene/Cesium3DTileset.js
@@ -29,6 +29,7 @@ define([
         './Cesium3DTileContentState',
         './Cesium3DTileOptimizations',
         './Cesium3DTileRefine',
+        './Cesium3DTilesetAsyncTraversal',
         './Cesium3DTilesetCache',
         './Cesium3DTilesetStatistics',
         './Cesium3DTilesetTraversal',
@@ -73,6 +74,7 @@ define([
         Cesium3DTileContentState,
         Cesium3DTileOptimizations,
         Cesium3DTileRefine,
+        Cesium3DTilesetAsyncTraversal,
         Cesium3DTilesetCache,
         Cesium3DTilesetStatistics,
         Cesium3DTilesetTraversal,
@@ -204,6 +206,7 @@ define([
         this._statistics = new Cesium3DTilesetStatistics();
         this._statisticsLastRender = new Cesium3DTilesetStatistics();
         this._statisticsLastPick = new Cesium3DTilesetStatistics();
+        this._statisticsLastAsync = new Cesium3DTilesetStatistics();
 
         this._tilesLoaded = false;
         this._initialTilesLoaded = false;
@@ -1707,9 +1710,9 @@ define([
     function updateTiles(tileset, frameState) {
         tileset._styleEngine.applyStyle(tileset, frameState);
 
+        var statistics = tileset._statistics;
         var passes = frameState.passes;
         var isRender = passes.render;
-        var statistics = tileset._statistics;
         var commandList = frameState.commandList;
         var numberOfInitialCommands = commandList.length;
         var selectedTiles = tileset._selectedTiles;
@@ -1899,69 +1902,76 @@ define([
 
     ///////////////////////////////////////////////////////////////////////////
 
-    /**
-     * @private
-     */
-    Cesium3DTileset.prototype.update = function(frameState) {
+    function update(tileset, frameState) {
         if (frameState.mode === SceneMode.MORPHING) {
-            return;
+            return false;
         }
 
-        if (!this.show || !this.ready) {
-            return;
+        if (!tileset.show || !tileset.ready) {
+            return false;
         }
 
-        if (!defined(this._loadTimestamp)) {
-            this._loadTimestamp = JulianDate.clone(frameState.time);
+        if (!defined(tileset._loadTimestamp)) {
+            tileset._loadTimestamp = JulianDate.clone(frameState.time);
         }
 
         // Update clipping planes
-        var clippingPlanes = this._clippingPlanes;
-        this._clippingPlanesOriginMatrixDirty = true;
+        var clippingPlanes = tileset._clippingPlanes;
+        tileset._clippingPlanesOriginMatrixDirty = true;
         if (defined(clippingPlanes) && clippingPlanes.enabled) {
             clippingPlanes.update(frameState);
         }
 
-        this._timeSinceLoad = Math.max(JulianDate.secondsDifference(frameState.time, this._loadTimestamp) * 1000, 0.0);
+        tileset._timeSinceLoad = Math.max(JulianDate.secondsDifference(frameState.time, tileset._loadTimestamp) * 1000, 0.0);
 
-        this._skipLevelOfDetail = this.skipLevelOfDetail && !defined(this._classificationType) && !this._disableSkipLevelOfDetail && !this._allTilesAdditive;
+        tileset._skipLevelOfDetail = tileset.skipLevelOfDetail && !defined(tileset._classificationType) && !tileset._disableSkipLevelOfDetail && !tileset._allTilesAdditive;
 
         // Do out-of-core operations (new content requests, cache removal,
         // process new tiles) only during the render pass.
         var passes = frameState.passes;
         var isRender = passes.render;
         var isPick = passes.pick;
+        var isAsync = passes.async;
 
-        var statistics = this._statistics;
+        var statistics = tileset._statistics;
         statistics.clear();
 
-        if (this.dynamicScreenSpaceError) {
-            updateDynamicScreenSpaceError(this, frameState);
+        if (tileset.dynamicScreenSpaceError) {
+            updateDynamicScreenSpaceError(tileset, frameState);
         }
 
         if (isRender) {
-            this._cache.reset();
+            tileset._cache.reset();
+        }
+
+        var ready;
+
+        if (isAsync) {
+            ready = Cesium3DTilesetAsyncTraversal.selectTiles(tileset, frameState);
+        } else {
+            ready = Cesium3DTilesetTraversal.selectTiles(tileset, frameState);
         }
 
-        Cesium3DTilesetTraversal.selectTiles(this, frameState);
+        if (isRender || isAsync) {
+            requestTiles(tileset);
+        }
 
         if (isRender) {
-            requestTiles(this);
-            processTiles(this, frameState);
+            processTiles(tileset, frameState);
         }
 
-        updateTiles(this, frameState);
+        updateTiles(tileset, frameState);
 
         if (isRender) {
-            unloadTiles(this);
+            unloadTiles(tileset);
 
             // Events are raised (added to the afterRender queue) here since promises
             // may resolve outside of the update loop that then raise events, e.g.,
             // model's readyPromise.
-            raiseLoadProgressEvent(this, frameState);
+            raiseLoadProgressEvent(tileset, frameState);
 
             if (statistics.selected !== 0) {
-                var credits = this._credits;
+                var credits = tileset._credits;
                 if (defined(credits)) {
                     var length = credits.length;
                     for (var i = 0; i < length; i++) {
@@ -1972,8 +1982,24 @@ define([
         }
 
         // Update last statistics
-        var statisticsLast = isPick ? this._statisticsLastPick : this._statisticsLastRender;
+        var statisticsLast = isAsync ? tileset._statisticsLastAsync : (isPick ? tileset._statisticsLastPick : tileset._statisticsLastRender);
         Cesium3DTilesetStatistics.clone(statistics, statisticsLast);
+
+        return ready;
+    }
+
+    /**
+     * @private
+     */
+    Cesium3DTileset.prototype.update = function(frameState) {
+        update(this, frameState);
+    };
+
+    /**
+     * @private
+     */
+    Cesium3DTileset.prototype.updateAsync = function(frameState) {
+        return update(this, frameState);
     };
 
     /**