Fixed Rectangle.union to take rectangles crossing the IDL into account.

CHANGES.md

@@ -5,6 +5,7 @@ Change Log
 
 * Added the ability to blend a `Model` with a color/translucency. Added `color`, `colorBlendMode`, and `colorBlendAmount` properties to `Model`, `ModelGraphics`, and CZML. Added `ColorBlendMode` enum. [#4547](https://github.com/AnalyticalGraphicsInc/cesium/pull/4547)
 * Fixed tooltips for gallery thumbnails in Sandcastle [#4702](https://github.com/AnalyticalGraphicsInc/cesium/pull/4702)
+* Fixed `Rectangle.union` to correctly account for rectangles that cross the IDL [#4732](https://github.com/AnalyticalGraphicsInc/cesium/pull/4732).
 * Fixed texture rotation for `RectangleGeometry` [#2737](https://github.com/AnalyticalGraphicsInc/cesium/issues/2737)
 
 ### 1.28 - 2016-12-01

Source/Core/Rectangle.js

@@ -723,9 +723,30 @@ define([
             result = new Rectangle();
         }
 
-        result.west = Math.min(rectangle.west, otherRectangle.west);
+        var rectangleEast = rectangle.east;
+        var rectangleWest = rectangle.west;
+
+        var otherRectangleEast = otherRectangle.east;
+        var otherRectangleWest = otherRectangle.west;
+
+        if (rectangleEast < rectangleWest && otherRectangleEast > 0.0) {
+            rectangleEast += CesiumMath.TWO_PI;
+        } else if (otherRectangleEast < otherRectangleWest && rectangleEast > 0.0) {
+            otherRectangleEast += CesiumMath.TWO_PI;
+        }
+
+        if (rectangleEast < rectangleWest && otherRectangleWest < 0.0) {
+            otherRectangleWest += CesiumMath.TWO_PI;
+        } else if (otherRectangleEast < otherRectangleWest && rectangleWest < 0.0) {
+            rectangleWest += CesiumMath.TWO_PI;
+        }
+
+        var west = CesiumMath.convertLongitudeRange(Math.min(rectangleWest, otherRectangleWest));
+        var east = CesiumMath.convertLongitudeRange(Math.max(rectangleEast, otherRectangleEast));
+
+        result.west = west;
         result.south = Math.min(rectangle.south, otherRectangle.south);
-        result.east = Math.max(rectangle.east, otherRectangle.east);
+        result.east = east;
         result.north = Math.max(rectangle.north, otherRectangle.north);
 
         return result;

Specs/Core/RectangleSpec.js

@@ -577,6 +577,30 @@ defineSuite([
         expect(returnedResult).toEqual(expected);
     });
 
+    it('union works with first rectangle crossing the IDL', function() {
+        var rectangle1 = new Rectangle(0.5, 0.1, -0.5, 0.9);
+        var rectangle2 = new Rectangle(-0.85, 0.0, -0.4, 0.8);
+        var expected = new Rectangle(0.5, 0.0, -0.4, 0.9);
+        var returnedResult = Rectangle.union(rectangle1, rectangle2);
+        expect(returnedResult).toEqualEpsilon(expected, CesiumMath.EPSILON15);
+    });
+
+    it('union works with second rectangle crossing the IDL', function() {
+        var rectangle1 = new Rectangle(0.5, 0.1, 0.75, 0.9);
+        var rectangle2 = new Rectangle(0.6, 0.0, -0.2, 0.8);
+        var expected = new Rectangle(0.5, 0.0, -0.2, 0.9);
+        var returnedResult = Rectangle.union(rectangle1, rectangle2);
+        expect(returnedResult).toEqualEpsilon(expected, CesiumMath.EPSILON15);
+    });
+
+    it('union works with both rectangles crossing the IDL', function() {
+        var rectangle1 = new Rectangle(0.5, 0.1, -0.4, 0.9);
+        var rectangle2 = new Rectangle(0.4, 0.0, -0.5, 0.8);
+        var expected = new Rectangle(0.4, 0.0, -0.4, 0.9);
+        var returnedResult = Rectangle.union(rectangle1, rectangle2);
+        expect(returnedResult).toEqualEpsilon(expected, CesiumMath.EPSILON15);
+    });
+
     it('expand works if rectangle needs to grow right', function() {
         var rectangle = new Rectangle(0.5, 0.1, 0.75, 0.9);
         var cartographic = new Cartographic(0.85, 0.5);