Update Readme with Architecture diagram

README.md

@@ -6,11 +6,15 @@ Cesium Native is a set of C++ libraries for 3D geosaptial, including:
 * lightweight glTF serialization and deserialization, and
 * high-precision 3D geospatial math types and functions, including support for global-scale WGS84 ellipsoids.
 
-Currently Cesium Native is used to develop [Cesium for Unreal](https://github.com/CesiumGS/cesium-unreal). In the future, we plan for Cesium Native to be a foundational layer for any 3D geospatial software, especially those that want to stream 3D Tiles.
-
 [![License](https://img.shields.io/:license-Apache_2.0-blue.svg)](https://github.com/CesiumGS/cesium-native/blob/main/LICENSE)
 [![Build Status](https://api.travis-ci.com/CesiumGS/cesium-native.svg?token=z6LPvn37d5E37hGcTgua&branch=main&status=passed)](https://travis-ci.com/CesiumGS/cesium-native)
 
+Currently Cesium Native is used to develop [Cesium for Unreal](https://github.com/CesiumGS/cesium-unreal). In the future, we plan for Cesium Native to be a foundational layer for any 3D geospatial software, especially those that want to stream 3D Tiles.
+
+![Cesium for Unreal Architecture](./doc/unreal-architecture.png)
+*<p align="center">A high-level architecture of Cesium for Unreal, Cesium Native and Unreal Engine streaming content from Cesium ion.</p>*
+
+
 ### :card_file_box:Libraries Overview
 
 | Library | Description |
@@ -24,6 +28,7 @@ Currently Cesium Native is used to develop [Cesium for Unreal](https://github.co
 | **CesiumIonClient** | Functions to access [Cesium ion](https://cesium.com/cesium-ion/) accounts and 3D tilesets using ion's REST API. |
 | **CesiumUtility** | Utility functions for JSON parsing, URI processing, etc. |
 
+
 ### :green_book:License
 
 [Apache 2.0](http://www.apache.org/licenses/LICENSE-2.0.html). Cesium Native is free for both commercial and non-commercial use.