Merge pull request #3165 from AnalyticalGraphicsInc/sphere-from-orien…

…ted-box

Added BoundingSphere.fromOrientedBoundingBox function

CHANGES.md

@@ -6,6 +6,7 @@ Change Log
 * Fixed an issue where the sun texture is not generated correctly on some mobile devices. [#3141](https://github.com/AnalyticalGraphicsInc/cesium/issues/3141)
 * Fixed a bug in the deprecated `jsonp` that prevented it from returning a promise.  Its replacement, `loadJsonp`, was unaffected.
 * Fixed glTF implementation to read the version as a string as per the specification and to correctly handle backwards compatibility for axis-angle rotations in glTF 0.8 models.
+* Added `BoundingSphere.fromOrientedBoundingBox` function.
 * Fixed a bug that caused setting `Entity.parent` to `undefined` to throw an exception. [#3169](https://github.com/AnalyticalGraphicsInc/cesium/issues/3169)
 * Added `Model.maximumScale` and `ModelGraphics.maximumScale` properties, giving an upper limit for minimumPixelSize.
 * Entities have a reference to their entity collection.

Source/Core/BoundingSphere.js

@@ -10,6 +10,7 @@ define([
         './GeographicProjection',
         './Intersect',
         './Interval',
+        './Matrix3',
         './Matrix4',
         './Plane',
         './Rectangle'
@@ -24,6 +25,7 @@ define([
         GeographicProjection,
         Intersect,
         Interval,
+        Matrix3,
         Matrix4,
         Plane,
         Rectangle) {
@@ -590,6 +592,37 @@ define([
         return result;
     };
 
+    var fromOrientedBoundingBoxScratchU = new Cartesian3();
+    var fromOrientedBoundingBoxScratchV = new Cartesian3();
+    var fromOrientedBoundingBoxScratchW = new Cartesian3();
+
+    /**
+     * Computes a tight-fitting bounding sphere enclosing the provided oriented bounding box.
+     *
+     * @param {OrientedBoundingBox} orientedBoundingBox The oriented bounding box.
+     * @param {BoundingSphere} [result] The object onto which to store the result.
+     * @returns {BoundingSphere} The modified result parameter or a new BoundingSphere instance if none was provided.
+     */
+    BoundingSphere.fromOrientedBoundingBox = function(orientedBoundingBox, result) {
+        if (!defined(result)) {
+            result = new BoundingSphere();
+        }
+
+        var halfAxes = orientedBoundingBox.halfAxes;
+        var u = Matrix3.getColumn(halfAxes, 0, fromOrientedBoundingBoxScratchU);
+        var v = Matrix3.getColumn(halfAxes, 1, fromOrientedBoundingBoxScratchV);
+        var w = Matrix3.getColumn(halfAxes, 2, fromOrientedBoundingBoxScratchW);
+
+        var uHalf = Cartesian3.magnitude(u);
+        var vHalf = Cartesian3.magnitude(v);
+        var wHalf = Cartesian3.magnitude(w);
+
+        result.center = Cartesian3.clone(orientedBoundingBox.center, result.center);
+        result.radius = Math.max(uHalf, vHalf, wHalf);
+
+        return result;
+    };
+
     /**
      * Duplicates a BoundingSphere instance.
      *

Source/Core/OrientedBoundingBox.js

@@ -611,9 +611,9 @@ define([
     /**
      * Determines whether or not a bounding box is hidden from view by the occluder.
      *
-     * @param {OrientedBoundingBox} sphere The bounding box surrounding the occludee object.
+     * @param {OrientedBoundingBox} box The bounding box surrounding the occludee object.
      * @param {Occluder} occluder The occluder.
-     * @returns {Boolean} <code>true</code> if the sphere is not visible; otherwise <code>false</code>.
+     * @returns {Boolean} <code>true</code> if the box is not visible; otherwise <code>false</code>.
      */
     OrientedBoundingBox.isOccluded = function(box, occluder) {
         //>>includeStart('debug', pragmas.debug);
@@ -625,18 +625,7 @@ define([
         }
         //>>includeEnd('debug');
 
-        var halfAxes = box.halfAxes;
-        var u = Matrix3.getColumn(halfAxes, 0, scratchCartesianU);
-        var v = Matrix3.getColumn(halfAxes, 1, scratchCartesianV);
-        var w = Matrix3.getColumn(halfAxes, 2, scratchCartesianW);
-
-        var uHalf = Cartesian3.magnitude(u);
-        var vHalf = Cartesian3.magnitude(v);
-        var wHalf = Cartesian3.magnitude(w);
-
-        var sphere = scratchBoundingSphere;
-        sphere.center = Cartesian3.clone(box.center, sphere.center);
-        sphere.radius = Math.max(uHalf, vHalf, wHalf);
+        var sphere = BoundingSphere.fromOrientedBoundingBox(box, scratchBoundingSphere);
 
         return !occluder.isBoundingSphereVisible(sphere);
     };

Specs/Core/BoundingSphereSpec.js

@@ -10,6 +10,7 @@ defineSuite([
         'Core/Interval',
         'Core/Math',
         'Core/Matrix4',
+        'Core/OrientedBoundingBox',
         'Core/Plane',
         'Core/Rectangle',
         'Specs/createPackableSpecs'
@@ -24,6 +25,7 @@ defineSuite([
         Interval,
         CesiumMath,
         Matrix4,
+        OrientedBoundingBox,
         Plane,
         Rectangle,
         createPackableSpecs) {
@@ -386,6 +388,21 @@ defineSuite([
         expect(sphere).toEqual(expected);
     });
 
+    it('fromOrientedBoundingBox works with a result', function() {
+        var box = OrientedBoundingBox.fromPoints(getPositions());
+        var expected = new BoundingSphere(positionsCenter, positionsRadius);
+        var sphere = new BoundingSphere();
+        BoundingSphere.fromOrientedBoundingBox(box, sphere);
+        expect(sphere).toEqual(expected);
+    });
+
+    it('fromOrientedBoundingBox works without a result parameter', function() {
+        var box = OrientedBoundingBox.fromPoints(getPositions());
+        var expected = new BoundingSphere(positionsCenter, positionsRadius);
+        var sphere = BoundingSphere.fromOrientedBoundingBox(box);
+        expect(sphere).toEqual(expected);
+    });
+
     it('intersectPlane with sphere on the positive side of a plane', function() {
         var sphere = new BoundingSphere(Cartesian3.ZERO, 0.5);
         var normal = Cartesian3.negate(Cartesian3.UNIT_X, new Cartesian3());