classref: Sync with current master branch (029aade)

classes/class_packedvector3array.rst

@@ -19,6 +19,10 @@ Description
 
 An array specifically designed to hold :ref:`Vector3<class_Vector3>`. Packs data tightly, so it saves memory for large array sizes.
 
+\ **Differences between packed arrays, typed arrays, and untyped arrays:** Packed arrays are generally faster to iterate on and modify compared to a typed array of the same type (e.g. **PackedVector3Array** versus ``Array[Vector3]``). Also, packed arrays consume less memory. As a downside, packed arrays are less flexible as they don't offer as many convenience methods such as :ref:`Array.map<class_Array_method_map>`. Typed arrays are in turn faster to iterate on and modify than untyped arrays.
+
+\ **Note:** Packed arrays are always passed by reference. To get a copy of an array that can be modified independently of the original array, use :ref:`duplicate<class_PackedVector3Array_method_duplicate>`. This is *not* the case for built-in properties and methods. The returned packed array of these are a copies, and changing it will *not* affect the original value. To update a built-in property you need to modify the returned array, and then assign it to the property again.
+
 .. note::
 
 	There are notable differences when using this API with C#. See :ref:`doc_c_sharp_differences` for more information.