common extensions and some utilities

Runtime/Engine/Code/Extensions/Vector3Ex.cs

@@ -0,0 +1,11 @@
+using UnityEngine;
+
+namespace RebootKit.Engine.Extensions {
+    public static class Vector3Ex {
+        public static Vector3 With(this Vector3 vec, float? x = null, float? y = null, float? z = null) {
+            return new Vector3(x ?? vec.x,
+                               y ?? vec.y,
+                               z ?? vec.z);
+        }
+    }
+}