Merge pull request #4982 from AnalyticalGraphicsInc/zoom-auto-reset

Auto-reset the zoom after zooming past a target.

Author: pjcozzi

CHANGES.md

@@ -2,10 +2,11 @@ Change Log
 ==========
 
 ### 1.31 - 2017-03-01
+
 * Deprecated
-  * `ArcGisImageServerTerrainProvider` will be removed in 1.32 due to missing TIFF support in web browsers.
+   * `ArcGisImageServerTerrainProvider` will be removed in 1.32 due to missing TIFF support in web browsers.
 * Breaking changes
-  * Corrected spelling of `Color.FUCHSIA` from `Color.FUSCHIA`
+   * Corrected spelling of `Color.FUCHSIA` from `Color.FUSCHIA`. [#4977](https://github.com/AnalyticalGraphicsInc/cesium/pull/4977)
 * Added support to `DebugCameraPrimitive` to draw multifrustum planes. The attribute `debugShowFrustumPlanes` of `Scene` and `frustumPlanes` of `CesiumInspector` toggles this. `FrameState` has been augmented to include `frustumSplits` which is a `Number[]` of the near/far planes of the camera frustums.
 * Enable rendering `GroundPrimitives` on hardware without the `EXT_frag_depth` extension; however, this could cause artifacts for certain viewing angles.
 * Added compressed texture support. [#4758](https://github.com/AnalyticalGraphicsInc/cesium/pull/4758)
@@ -14,6 +15,7 @@ Change Log
    * Added new `PixelFormat` and `WebGLConstants` enums from WebGL extensions `WEBGL_compressed_s3tc`, `WEBGL_compressed_texture_pvrtc`, and `WEBGL_compressed_texture_etc1`.
    * Added `CompressedTextureBuffer`.
 * Improved `RectangleGeometry` by skipping unecessary logic in the code [#4948](https://github.com/AnalyticalGraphicsInc/cesium/pull/4948)
+* Fixed an issue where the camera would zoom past an object and flip to the other side of the globe. [#4967](https://github.com/AnalyticalGraphicsInc/cesium/pull/4967) and [#4982](https://github.com/AnalyticalGraphicsInc/cesium/pull/4982)
 
 ### 1.30 - 2017-02-01
 

Source/Scene/ScreenSpaceCameraController.js

@@ -576,6 +576,9 @@ define([
 
                         var alphaDot = Cartesian3.dot(cameraPositionNormal, positionToTargetNormal);
                         if (alphaDot >= 0.0) {
+                            // We zoomed past the target, and this zoom is not valid anymore.
+                            // This line causes the next zoom movement to pick a new starting point.
+                            object._zoomMouseStart.x = -1;
                             return;
                         }
                         var alpha = Math.acos(-alphaDot);