CesiumGS · kring · Sep 18, 2014 · Sep 1, 2014 · Sep 1, 2014 · Sep 2, 2014
diff --git a/Apps/Sandcastle/gallery/Profile Half Dome.html b/Apps/Sandcastle/gallery/Profile Half Dome.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="utf-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1">  <!-- Use Chrome Frame in IE -->
+    <meta name="viewport" content="width=device-width, height=device-height, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no">
+    <meta name="description" content="Use Viewer to start building new applications or easily embed Cesium into existing applications.">
+    <meta name="cesium-sandcastle-labels" content="Profiling">
+    <title>Cesium Demo</title>
+    <script type="text/javascript" src="../Sandcastle-header.js"></script>
+    <script type="text/javascript" src="../../../ThirdParty/requirejs-2.1.9/require.js"></script>
+    <script type="text/javascript">
+    require.config({
+        baseUrl : '../../../Source',
+        waitSeconds : 60
+    });
+    </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 cesiumTerrainProviderMeshes = new Cesium.CesiumTerrainProvider({
+        url : '//cesiumjs.org/stk-terrain/tilesets/world/tiles'
+    });
+
+    var viewer = new Cesium.Viewer('cesiumContainer');
+    var scene = viewer.scene;
+    scene.terrainProvider = cesiumTerrainProviderMeshes;
+
+    var setCamera = function() {
+        var eye = new Cesium.Cartesian3(-2496304.1498512086, -4391818.97382059, 3884176.4503971986);
+        var target = Cesium.Cartesian3.add(eye, new Cesium.Cartesian3(0.9279518715011381, -0.29488412129953234, -0.22792252890604328), new Cesium.Cartesian3());
+        var up = new Cesium.Cartesian3(-0.11836693744723503, -0.8130611584421428, 0.5700182635106171);
+        scene.camera.lookAt(eye, target, up);
+    };
+
+    setCamera();
+
+    // Keep updating the camera so it doesn't get pushed above low resolution terrain.
+    setInterval(setCamera, 1000);
+    //Sandcastle_End
+    Sandcastle.finishedLoading();
+}
+if (typeof Cesium !== "undefined") {
+    startup(Cesium);
+} else if (typeof require === "function") {
+    require(["Cesium"], startup);
+}
+</script>
+</body>
+</html>
diff --git a/CHANGES.md b/CHANGES.md
@@ -4,6 +4,7 @@ Change Log
 ### 1.2 - 2014-10-01
 
 * Eliminated imagery artifacts at some zoom levels due to Mercator reprojection.
+* Added `TerrainProvider.getTileDataAvailable` to improve tile loading performance when camera starts near globe.
 
 ### 1.1 - 2014-09-02
 

diff --git a/Source/Core/ArcGisImageServerTerrainProvider.js b/Source/Core/ArcGisImageServerTerrainProvider.js
@@ -244,5 +244,17 @@ define([
         return this._levelZeroMaximumGeometricError / (1 << level);
     };
 
+    /**
+     * Determines whether data for a tile is available to be loaded.
+     *
+     * @param {Number} x The X coordinate of the tile for which to request geometry.
+     * @param {Number} y The Y coordinate of the tile for which to request geometry.
+     * @param {Number} level The level of the tile for which to request geometry.
+     * @returns {Number} Undefined if not supported, otherwise true or false.
+     */
+    ArcGisImageServerTerrainProvider.prototype.getTileDataAvailable = function(x, y, level) {
+        return undefined;
+    };
+
     return ArcGisImageServerTerrainProvider;
 });
diff --git a/Source/Core/CesiumTerrainProvider.js b/Source/Core/CesiumTerrainProvider.js
@@ -636,5 +636,27 @@ define([
         return false;
     }
 
+    /**
+     * Determines whether data for a tile is available to be loaded.
+     *
+     * @param {Number} x The X coordinate of the tile for which to request geometry.
+     * @param {Number} y The Y coordinate of the tile for which to request geometry.
+     * @param {Number} level The level of the tile for which to request geometry.
+     * @returns {Number} Undefined if not supported, otherwise true or false.
+     */
+    CesiumTerrainProvider.prototype.getTileDataAvailable = function(x, y, level) {
+        var available = this._availableTiles;
+
+        if (!available || available.length === 0) {
+            return undefined;
+        } else {
+            if (level >= available.length) {
+                return false;
+            }
+            var levelAvailable = available[level];
+            return isTileInRange(levelAvailable, x, y);
+        }
+    };
+
     return CesiumTerrainProvider;
 });
diff --git a/Source/Core/EllipsoidTerrainProvider.js b/Source/Core/EllipsoidTerrainProvider.js
@@ -166,5 +166,17 @@ define([
         return this._levelZeroMaximumGeometricError / (1 << level);
     };
 
+    /**
+     * Determines whether data for a tile is available to be loaded.
+     *
+     * @param {Number} x The X coordinate of the tile for which to request geometry.
+     * @param {Number} y The Y coordinate of the tile for which to request geometry.
+     * @param {Number} level The level of the tile for which to request geometry.
+     * @returns {Number} Undefined if not supported, otherwise true or false.
+     */
+    EllipsoidTerrainProvider.prototype.getTileDataAvailable = function(x, y, level) {
+        return undefined;
+    };
+
     return EllipsoidTerrainProvider;
 });
diff --git a/Source/Core/TerrainProvider.js b/Source/Core/TerrainProvider.js
@@ -192,5 +192,16 @@ define([
      */
     TerrainProvider.prototype.getLevelMaximumGeometricError = DeveloperError.throwInstantiationError;
 
+    /**
+     * Determines whether data for a tile is available to be loaded.
+     * @function
+     *
+     * @param {Number} x The X coordinate of the tile for which to request geometry.
+     * @param {Number} y The Y coordinate of the tile for which to request geometry.
+     * @param {Number} level The level of the tile for which to request geometry.
+     * @returns {Number} Undefined if not supported by the terrain provider, otherwise true or false.
+     */
+    TerrainProvider.prototype.getTileDataAvailable = DeveloperError.throwInstantiationError;
+
     return TerrainProvider;
 });
diff --git a/Source/Core/VRTheWorldTerrainProvider.js b/Source/Core/VRTheWorldTerrainProvider.js
@@ -335,5 +335,17 @@ define([
         return !Rectangle.isEmpty(Rectangle.intersectWith(tileRectangle, rectangle, rectangleScratch));
     }
 
+    /**
+     * Determines whether data for a tile is available to be loaded.
+     *
+     * @param {Number} x The X coordinate of the tile for which to request geometry.
+     * @param {Number} y The Y coordinate of the tile for which to request geometry.
+     * @param {Number} level The level of the tile for which to request geometry.
+     * @returns {Number} Undefined if not supported, otherwise true or false.
+     */
+    VRTheWorldTerrainProvider.prototype.getTileDataAvailable = function(x, y, level) {
+        return undefined;
+    };
+
     return VRTheWorldTerrainProvider;
 });
diff --git a/Source/Scene/GlobeSurfaceTile.js b/Source/Scene/GlobeSurfaceTile.js
@@ -378,7 +378,7 @@ define([
             surfaceTile.upsampledTerrain = new TileTerrain(upsampleTileDetails);
         }
 
-        if (isDataAvailable(tile)) {
+        if (isDataAvailable(tile, terrainProvider)) {
             surfaceTile.loadedTerrain = new TileTerrain();
         }
 
@@ -618,7 +618,15 @@ define([
         }
     }
 
-    function isDataAvailable(tile) {
+    function isDataAvailable(tile, terrainProvider) {
+
+        if (defined(terrainProvider.getTileDataAvailable)) {
+            var tileDataAvailable = terrainProvider.getTileDataAvailable(tile.x, tile.y, tile.level);
+            if (defined(tileDataAvailable)) {
+                return tileDataAvailable;
+            }
+        }
+
         var parent = tile.parent;
         if (!defined(parent)) {
             // Data is assumed to be available for root tiles.

diff --git a/Specs/Core/CesiumTerrainProviderSpec.js b/Specs/Core/CesiumTerrainProviderSpec.js
@@ -596,5 +596,42 @@ defineSuite([
                 }
             });
         });
+
+        it('supports getTileDataAvailable()', function() {
+            var baseUrl = 'made/up/url';
+
+            loadWithXhr.load = function(url, responseType, method, data, headers, deferred, overrideMimeType) {
+                return loadWithXhr.defaultLoad('Data/CesiumTerrainTileJson/tile.terrain', responseType, method, data, headers, deferred);
+            };
+
+            returnQuantizedMeshTileJson();
+
+            var terrainProvider = new CesiumTerrainProvider({
+                url : baseUrl
+            });
+
+            waitsFor(function() {
+                return terrainProvider.ready;
+            });
+
+            var loadedData;
+
+            runs(function() {
+                var promise = terrainProvider.requestTileGeometry(0, 0, 0);
+
+                when(promise, function(terrainData) {
+                    loadedData = terrainData;
+                });
+            });
+
+            waitsFor(function() {
+                return defined(loadedData);
+            }, 'request to complete');
+
+            runs(function() {
+                expect(terrainProvider.getTileDataAvailable(0, 0, 0)).toBe(true);
+                expect(terrainProvider.getTileDataAvailable(0, 0, 2)).toBe(false);
+            });
+        });
     });
 });
diff --git a/Specs/Core/EllipsoidTerrainProviderSpec.js b/Specs/Core/EllipsoidTerrainProviderSpec.js
@@ -1,10 +1,12 @@
 /*global defineSuite*/
 defineSuite([
         'Core/EllipsoidTerrainProvider',
+        'Core/TerrainProvider',
         'Specs/createContext',
         'Specs/destroyContext'
     ], function(
         EllipsoidTerrainProvider,
+        TerrainProvider,
         createContext,
         destroyContext) {
     "use strict";
@@ -20,6 +22,10 @@ defineSuite([
         destroyContext(context);
     });
 
+    it('conforms to TerrainProvider interface', function() {
+        expect(EllipsoidTerrainProvider).toConformToInterface(TerrainProvider);
+    });
+
     it('requestTileGeometry creates terrain data.', function() {
         var terrain = new EllipsoidTerrainProvider();
         var terrainData = terrain.requestTileGeometry(0, 0, 0);
@@ -31,4 +37,9 @@ defineSuite([
         expect(provider.errorEvent).toBeDefined();
         expect(provider.errorEvent).toBe(provider.errorEvent);
     });
+
+    it('returns undefined on getTileDataAvailable()', function() {
+        var provider = new EllipsoidTerrainProvider();
+        expect(provider.getTileDataAvailable()).toBeUndefined();
+    });
 }, 'WebGL');