(#35) Add Random.NextUnitVector3

X10D/src/RandomExtensions/RandomExtensions.Numerics.cs

@@ -31,6 +31,33 @@ namespace X10D.RandomExtensions
 
             return new Vector2(x, y);
         }
+
+        /// <summary>
+        ///     Returns a <see cref="Vector3" /> with magnitude 1 whose components indicate a random point on the unit sphere. 
+        /// </summary>
+        /// <param name="random">The <see cref="System.Random" /> instance</param>
+        /// <returns>
+        ///     A <see cref="Vector3" /> whose <see cref="Vector3.Length()" /> returns 1, and whose components indicate a random
+        ///     point on the unit sphere.
+        /// </returns>
+        public static Vector3 NextUnitVector3(this Random random)
+        {
+            if (random is null)
+            {
+                throw new ArgumentNullException(nameof(random));
+            }
+
+            var seed = random.Next();
+            var seededRandom = new Random(seed);
+
+            var angle = seededRandom.NextSingle(0, 360).DegreesToRadians();
+            var z = seededRandom.NextSingle(-1, 1);
+            var mp = MathF.Sqrt(1 - z * z);
+            var x = mp * MathF.Cos(angle);
+            var y = mp * MathF.Sin(angle);
+
+            return new Vector3(x, y, z);
+        }
     }
 }