Fix #1749 by adding an OIT flag.

CHANGES.md

@@ -3,6 +3,7 @@ Change Log
 
 ### 1.2 - 2014-10-01
 
+* Added a constructor option to `Scene`, `CesiumWidget`, and `Viewer` to disable order independent translucency.
 * Eliminated imagery artifacts at some zoom levels due to Mercator reprojection.
 * Fixed a bug in `Model` where the wrong animations could be used when the model was created from glTF JSON instead of 
 a url to a glTF file.  [#2078](https://github.com/AnalyticalGraphicsInc/cesium/issues/2078)

Source/Scene/Scene.js

@@ -154,6 +154,7 @@ define([
      * @param {Object} [options.contextOptions] Context and WebGL creation properties.  See details above.
      * @param {Element} [options.creditContainer] The HTML element in which the credits will be displayed.
      * @param {MapProjection} [options.mapProjection=new GeographicProjection()] The map projection to use in 2D and Columbus View modes.
+     * @param {Boolean} [options.orderIndependentTranslucency=true] If true and the configuration supports it, use order independent translucency.
      * @param {Boolean} [options.scene3DOnly=false] If true, optimizes memory use and performance for 3D mode but disables the ability to use 2D or Columbus View.     *
      * @see CesiumWidget
      * @see {@link http://www.khronos.org/registry/webgl/specs/latest/#5.2|WebGLContextAttributes}
@@ -214,7 +215,7 @@ define([
         this._frustumCommandsList = [];
         this._overlayCommandList = [];
 
-        this._oit = new OIT(context);
+        this._oit = defaultValue(options.orderIndependentTranslucency, true) ? new OIT(context) : undefined;
         this._executeOITFunction = undefined;
 
         this._fxaa = new FXAA();
@@ -731,6 +732,19 @@ define([
             }
         },
 
+        /**
+         * Gets whether or not the scene has order independent translucency enabled.
+         * Note that this only reflects the original construction option, and there are
+         * other factors that could prevent OIT from functioning on a given system configuration.
+         * @memberof Scene.prototype
+         * @type {Boolean}
+         */
+        orderIndependentTranslucency : {
+            get : function() {
+                return defined(this._oit);
+            }
+        },
+
         /**
          * Gets the unique identifier for this scene.
          * @memberof Scene.prototype
@@ -1175,7 +1189,7 @@ define([
             }
         }
 
-        var useOIT = !picking && renderTranslucentCommands && scene._oit.isSupported();
+        var useOIT = !picking && renderTranslucentCommands && defined(scene._oit) && scene._oit.isSupported();
         if (useOIT) {
             scene._oit.update(context);
             scene._oit.clear(context, passState, clearColor);
@@ -1700,7 +1714,9 @@ define([
 
         this._transitioner.destroy();
 
-        this._oit.destroy();
+        if (defined(this._oit)) {
+            this._oit.destroy();
+        }
         this._fxaa.destroy();
 
         this._context = this._context && this._context.destroy();

Source/Widgets/CesiumWidget/CesiumWidget.js

@@ -138,6 +138,7 @@ define([
      * @param {SkyBox} [options.skyBox] The skybox used to render the stars.  When <code>undefined</code>, the default stars are used.
      * @param {SceneMode} [options.sceneMode=SceneMode.SCENE3D] The initial scene mode.
      * @param {Boolean} [options.scene3DOnly=false] When <code>true</code>, each geometry instance will only be rendered in 3D to save GPU memory.
+     * @param {Boolean} [options.orderIndependentTranslucency=true] If true and the configuration supports it, use order independent translucency.
      * @param {MapProjection} [options.mapProjection=new GeographicProjection()] The map projection to use in 2D and Columbus View modes.
      * @param {Boolean} [options.useDefaultRenderLoop=true] True if this widget should control the render loop, false otherwise.
      * @param {Number} [options.targetFrameRate] The target frame rate when using the default render loop.
@@ -233,6 +234,7 @@ define([
                 contextOptions : options.contextOptions,
                 creditContainer : creditContainer,
                 mapProjection : options.mapProjection,
+                orderIndependentTranslucency : options.orderIndependentTranslucency,
                 scene3DOnly : defaultValue(options.scene3DOnly, false)
             });
             this._scene = scene;

Source/Widgets/Viewer/Viewer.js

@@ -97,6 +97,7 @@ define([
      * @param {Object} [options.contextOptions] Context and WebGL creation properties corresponding to <code>options</code> passed to {@link Scene}.
      * @param {SceneMode} [options.sceneMode=SceneMode.SCENE3D] The initial scene mode.
      * @param {MapProjection} [options.mapProjection=new GeographicProjection()] The map projection to use in 2D and Columbus View modes.
+     * @param {Boolean} [options.orderIndependentTranslucency=true] If true and the configuration supports it, use order independent translucency.
      * @param {Element|String} [options.creditContainer] The DOM element or ID that will contain the {@link CreditDisplay}.  If not specified, the credits are added to the bottom of the widget itself.
      * @param {DataSourceCollection} [options.dataSources=new DataSourceCollection()] The collection of data sources visualized by the widget.  If this parameter is provided,
                                      the instance is assumed to be owned by the caller and will not be destroyed when the viewer is destroyed.
@@ -224,6 +225,7 @@ Either specify options.terrainProvider instead or set options.baseLayerPicker to
             skyBox : options.skyBox,
             sceneMode : options.sceneMode,
             mapProjection : options.mapProjection,
+            orderIndependentTranslucency : options.orderIndependentTranslucency,
             contextOptions : options.contextOptions,
             useDefaultRenderLoop : options.useDefaultRenderLoop,
             targetFrameRate : options.targetFrameRate,

Specs/Widgets/CesiumWidget/CesiumWidgetSpec.js

@@ -181,6 +181,20 @@ defineSuite([
         expect(contextAttributes.preserveDrawingBuffer).toEqual(webglOptions.preserveDrawingBuffer);
     });
 
+    it('can enable Order Independent Translucency', function() {
+        widget = new CesiumWidget(container, {
+            orderIndependentTranslucency : true
+        });
+        expect(widget.scene.orderIndependentTranslucency).toBe(true);
+    });
+
+    it('can disable Order Independent Translucency', function() {
+        widget = new CesiumWidget(container, {
+            orderIndependentTranslucency : false
+        });
+        expect(widget.scene.orderIndependentTranslucency).toBe(false);
+    });
+
     it('throws if no container provided', function() {
         expect(function() {
             return new CesiumWidget(undefined);

Specs/Widgets/Viewer/ViewerSpec.js

@@ -312,6 +312,20 @@ defineSuite([
         expect(contextAttributes.preserveDrawingBuffer).toEqual(webglOptions.preserveDrawingBuffer);
     });
 
+    it('can enable Order Independent Translucency', function() {
+        viewer = new Viewer(container, {
+            orderIndependentTranslucency : true
+        });
+        expect(viewer.scene.orderIndependentTranslucency).toBe(true);
+    });
+
+    it('can disable Order Independent Translucency', function() {
+        viewer = new Viewer(container, {
+            orderIndependentTranslucency : false
+        });
+        expect(viewer.scene.orderIndependentTranslucency).toBe(false);
+    });
+
     it('can set scene mode', function() {
         viewer = new Viewer(container, {
             sceneMode : SceneMode.SCENE2D