Added Cesium.Math.cbrt

Author: lilleyse

CHANGES.md

@@ -5,6 +5,7 @@ Change Log
 
 ##### Additions :tada:
 * Added support for a promise to a resource for `CesiumTerrainProvider`, `createTileMapServiceImageryProvider` and `Cesium3DTileset` [#6204](https://github.com/AnalyticalGraphicsInc/cesium/pull/6204)
+* Added `Cesium.Math.cbrt`.
 
 ##### Fixes :wrench:
 * Fixed bug where AxisAlignedBoundingBox did not copy over center value when cloning an undefined result. [#6183](https://github.com/AnalyticalGraphicsInc/cesium/pull/6183)

Source/Core/Math.js

@@ -835,6 +835,20 @@ define([
         return Math.log(number) / Math.log(base);
     };
 
+    function cbrt(number) {
+        var result = Math.pow(Math.abs(number), 1.0 / 3.0);
+        return number < 0.0 ? -result : result;
+    }
+
+    /**
+     * Finds the cube root of a number.
+     * Returns NaN if <code>number</code> is not provided.
+     *
+     * @param {Number} [number] The number.
+     * @returns {Number} The result.
+     */
+    CesiumMath.cbrt = defined(Math.cbrt) ? Math.cbrt : cbrt;
+
     /**
      * @private
      */

Source/Scene/PointCloud3DTileContent.js

@@ -13,6 +13,7 @@ define([
         '../Core/DeveloperError',
         '../Core/FeatureDetection',
         '../Core/getStringFromTypedArray',
+        '../Core/Math',
         '../Core/Matrix3',
         '../Core/Matrix4',
         '../Core/oneTimeWarning',
@@ -51,6 +52,7 @@ define([
         DeveloperError,
         FeatureDetection,
         getStringFromTypedArray,
+        CesiumMath,
         Matrix3,
         Matrix4,
         oneTimeWarning,
@@ -466,7 +468,7 @@ define([
         // Typical use case is leaves, where lower estimates of interpoint distance might
         // lead to underattenuation.
         var sphereVolume = content._tile.contentBoundingVolume.boundingSphere.volume();
-        content._baseResolutionApproximation = Math.pow(sphereVolume / pointsLength, 1/3); // IE doesn't support cbrt
+        content._baseResolutionApproximation = CesiumMath.cbrt(sphereVolume / pointsLength);
     }
 
     var scratchPointSizeAndTilesetTimeAndGeometricErrorAndDepthMultiplier = new Cartesian4();

Specs/Core/MathSpec.js

@@ -434,4 +434,12 @@ defineSuite([
             CesiumMath.logBase(64, undefined);
         }).toThrowDeveloperError();
     });
+
+    it('cbrt', function() {
+        expect(CesiumMath.cbrt(27.0)).toEqual(3.0);
+        expect(CesiumMath.cbrt(-27.0)).toEqual(-3.0);
+        expect(CesiumMath.cbrt(0.0)).toEqual(0.0);
+        expect(CesiumMath.cbrt(1.0)).toEqual(1.0);
+        expect(CesiumMath.cbrt()).toEqual(NaN);
+    });
 });