Clone offset in adjustBoundingSphereOffset

Cloning the offset parameter of adjustBoundingSphereOffset results in no
argument reassignment in functions that use it. Because this
reassignment is not document and therefore unintentional it prevents
confusion when using the Camer api.

Author: jhnwsk

CONTRIBUTORS.md

@@ -239,3 +239,4 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for details on how to contribute to Cesiu
 * [Tinco Andringa](https://github.com/tinco)
 * [André Borud](https://github.com/andreborud)
 * [Nathan Schulte](https://github.com/nmschulte)
+* [Jan Wąsak](https://github.com/jhnwsk)

Source/Scene/Camera.js

@@ -2939,9 +2939,7 @@ import SceneMode from './SceneMode.js';
     var MINIMUM_ZOOM = 100.0;
 
     function adjustBoundingSphereOffset(camera, boundingSphere, offset) {
-        if (!defined(offset)) {
-            offset = HeadingPitchRange.clone(Camera.DEFAULT_OFFSET);
-        }
+        offset = HeadingPitchRange.clone(defined(offset) ? offset : Camera.DEFAULT_OFFSET);
 
         var minimumZoom = camera._scene.screenSpaceCameraController.minimumZoomDistance;
         var maximumZoom = camera._scene.screenSpaceCameraController.maximumZoomDistance;
@@ -3038,7 +3036,9 @@ import SceneMode from './SceneMode.js';
         options = defaultValue(options, defaultValue.EMPTY_OBJECT);
         var scene2D = this._mode === SceneMode.SCENE2D || this._mode === SceneMode.COLUMBUS_VIEW;
         this._setTransform(Matrix4.IDENTITY);
+        console.log(options.offset);
         var offset = adjustBoundingSphereOffset(this, boundingSphere, options.offset);
+        console.log(options.offset);
 
         var position;
         if (scene2D) {

Specs/Scene/CameraSpec.js

@@ -2633,6 +2633,23 @@ describe('Scene/Camera', function() {
         expect(camera.pitch).toEqualEpsilon(pitch, CesiumMath.EPSILON5);
     });
 
+    it('viewBoundingSphere does not modify offset.range when it is zero', function() {
+        scene.mode = SceneMode.SCENE3D;
+
+        var heading = CesiumMath.toRadians(45.0);
+        var pitch = CesiumMath.toRadians(-45.0);
+        var range = 0.0;
+        var offset = new HeadingPitchRange(heading, pitch, range);
+
+        var sphere = new BoundingSphere(Cartesian3.fromDegrees(-117.16, 32.71, 0.0), 10.0);
+        camera.viewBoundingSphere(sphere, offset);
+        camera._setTransform(Matrix4.IDENTITY);
+
+        expect(offset.heading).toEqual(CesiumMath.toRadians(45.0));
+        expect(offset.pitch).toEqual(CesiumMath.toRadians(-45.0));
+        expect(offset.range).toEqual(0.0);
+    });
+
     it('viewBoundingSphere in 2D', function() {
         var frustum = new OrthographicOffCenterFrustum();
         frustum.left = -10.0;
@@ -2748,6 +2765,20 @@ describe('Scene/Camera', function() {
         expect(CesiumMath.equalsEpsilon(distance, maxValue, 0.1)).toBe(true);
     });
 
+    it('flyToBoundingSphere does not modify options.offset range if it is zero ', function() {
+        scene.mode = SceneMode.SCENE3D;
+        var options = {
+            offset: new HeadingPitchRange(0.0, -1.5, 0.0)
+        };
+
+        var sphere = new BoundingSphere(Cartesian3.fromDegrees(-117.16, 32.71, 0.0), 100000.0);
+        camera.flyToBoundingSphere(sphere, options);
+
+        expect(options.offset.heading).toEqual(0.0);
+        expect(options.offset.pitch).toEqual(-1.5);
+        expect(options.offset.range).toEqual(0.0);
+    });
+
     it('distanceToBoundingSphere', function() {
         scene.mode = SceneMode.SCENE3D;