Math.rotateToAngle takes two angles (in radians), and an interpolation value, and returns a new angle, based on the shortest rotational distance between the two.

Author: photonstorm

README.md

@@ -314,6 +314,7 @@ You can read all about the philosophy behind Lazer [here](http://phaser.io/news/
 * Group.getAll will return all children in the Group, or a section of the Group, with the optional ability to test if the child has a property matching the given value or not.
 * Group.iterate has a new `returnType`: `RETURN_ALL`. This allows you to return all children that pass the iteration test in an array.
 * The property `checkCollision.none` in the ArcadePhysics.Body class was available, but never used internally. It is now used and checked by the `separate` method. By setting `checkCollision.none = true` you can disable all collision and overlap checks on a Body, but still retain its motion updates (thanks @samme #2661)
+* Math.rotateToAngle takes two angles (in radians), and an interpolation value, and returns a new angle, based on the shortest rotational distance between the two.
 
 ### Updates
 

src/math/Math.js

@@ -320,6 +320,57 @@ Phaser.Math = {
 
     },
 
+    /**
+    * Rotates currentAngle towards targetAngle, taking the shortest rotation distance.
+    * The lerp argument is the amount to rotate by in this call.
+    * 
+    * @method Phaser.Math#rotateToAngle
+    * @param {number} currentAngle - The current angle, in radians.
+    * @param {number} targetAngle - The target angle to rotate to, in radians.
+    * @param {number} [lerp=0.05] - The lerp value to add to the current angle.
+    * @return {number} The adjusted angle.
+    */
+    rotateToAngle: function (currentAngle, targetAngle, lerp) {
+
+        if (lerp === undefined) { lerp = 0.05; }
+
+        if (currentAngle === targetAngle)
+        {
+            return currentAngle;
+        }
+
+        if (Math.abs(targetAngle - currentAngle) <= lerp || Math.abs(targetAngle - currentAngle) >= (Phaser.Math.PI2 - lerp))
+        {
+            currentAngle = targetAngle;
+        }
+        else
+        {
+            if (Math.abs(targetAngle - currentAngle) > Math.PI)
+            {
+                if (targetAngle < currentAngle)
+                {
+                    targetAngle += Phaser.Math.PI2;
+                }
+                else
+                {
+                    targetAngle -= Phaser.Math.PI2;
+                }
+            }
+
+            if (targetAngle > currentAngle)
+            {
+                currentAngle += lerp;
+            }
+            else if (targetAngle < currentAngle)
+            {
+                currentAngle -= lerp;
+            }
+        }
+
+        return currentAngle;
+
+    },
+
     /**
     * Find the angle of a segment from (x1, y1) -> (x2, y2).
     * 

typescript/phaser.d.ts

@@ -2600,6 +2600,7 @@ declare module Phaser {
         static PI2: number;
         static radToDeg(radians: number): number;
         static reverseAngle(angleRed: number): number;
+        static rotateToAngle(currentAngle: number, targetAngle: number, lerp?: number): number;
         static roundAwayFromZero(value: number): number;
         static roundTo(value: number, place?: number, base?: number): number;
         static shear(n: number): number;