Use all url templates provided by terrain config file

CHANGES.md

@@ -18,6 +18,7 @@ Change Log
 * Added a workaround for Chrome 45, where the first character in a label with a small font size would not appear. [#3011](https://github.com/AnalyticalGraphicsInc/cesium/pull/3011)
 * Fixed issues causing the terrain and sky to disappear when the camera is near the surface. [#2415](https://github.com/AnalyticalGraphicsInc/cesium/issues/2415) and [#2271](https://github.com/AnalyticalGraphicsInc/cesium/issues/2271)
 * Changed the `ScreenSpaceCameraController.minimumZoomDistance` default from `20.0` to `1.0`.
+* Used all the template urls defined in the CesiumTerrain provider.[#3038](https://github.com/AnalyticalGraphicsInc/cesium/pull/3038)
 
 ### 1.13 - 2015-09-01
 

CONTRIBUTORS.md

@@ -65,5 +65,6 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
 * [Stéphane Lozier](https://github.com/slozier)
 * [Adam Cole](https://github.com/adamdavidcole)
 * [Tiffany Lu](https://github.com/tiffanylu)
+* [Olivier Terral](https://github.com/oterral)
 
 Also see [our contributors page](http://cesiumjs.org/contributors.html) for more information.

Source/Core/CesiumTerrainProvider.js

@@ -494,8 +494,7 @@ define([
 
         var tmsY = (yTiles - y - 1);
 
-        // Use the first URL template.  In the future we should use them all.
-        var url = urlTemplates[0].replace('{z}', level).replace('{x}', x).replace('{y}', tmsY);
+        var url = urlTemplates[(x + tmsY + level) % urlTemplates.length].replace('{z}', level).replace('{x}', x).replace('{y}', tmsY);
 
         var proxy = this._proxy;
         if (defined(proxy)) {

Specs/Core/CesiumTerrainProviderSpec.js

@@ -354,6 +354,29 @@ defineSuite([
     });
 
     describe('requestTileGeometry', function() {
+
+        it('uses multiple urls specified in layer.json', function() {
+            returnTileJson('Data/CesiumTerrainTileJson/MultipleUrls.tile.json');
+
+            var provider = new CesiumTerrainProvider({
+                url : 'made/up/url'
+            });
+
+            return pollToPromise(function() {
+                return provider.ready;
+            }).then(function() {
+                spyOn(loadWithXhr, 'load');
+                provider.requestTileGeometry(0, 0, 0);
+                expect(loadWithXhr.load.calls.mostRecent().args[0]).toContain('foo0.com');
+                provider.requestTileGeometry(1, 0, 0);
+                expect(loadWithXhr.load.calls.mostRecent().args[0]).toContain('foo1.com');
+                provider.requestTileGeometry(1, 1, 0);
+                expect(loadWithXhr.load.calls.mostRecent().args[0]).toContain('foo2.com');
+                provider.requestTileGeometry(1, 1, 1);
+                expect(loadWithXhr.load.calls.mostRecent().args[0]).toContain('foo3.com');
+            });
+        });
+
         it('uses the proxy if one is supplied', function() {
             var baseUrl = 'made/up/url';
 

Specs/Data/CesiumTerrainTileJson/MultipleUrls.tile.json

@@ -0,0 +1,12 @@
+{
+    "tilejson": "2.1.0",
+    "format" : "heightmap-1.0",
+    "version" : "1.0.0",
+    "scheme" : "tms",
+    "tiles" : [
+        "//foo0.com/bar/{z}/{x}/{y}.terrain?v={version}",
+        "//foo1.com/bar/{z}/{x}/{y}.terrain?v={version}",
+        "//foo2.com/bar/{z}/{x}/{y}.terrain?v={version}",
+        "//foo3.com/bar/{z}/{x}/{y}.terrain?v={version}"
+    ]
+}