This is part eight of a nine-part series that explores how to create a Unity application for a mobile device, using Augmented Reality and Azure Spatial Anchors

• In Part 1 we introduce the project, requirements, technologies and various AR concepts.
• In Part 2 we follow the steps in the project QuickStart guide.
• In Part 3 we create a basic Unity ARFoundation application.
• In Part 4 we look at one of the building blocks of AR - the “Placement Cursor”.
• In Part 5 we explore how the UI for the project works.
• In Part 6 we learn how Azure Spatial Anchors can be used in our project.
• In Part 7 we step up our game by looking at how we can add and move virtual scenery.
• In Part 8 we develop functionality that saves and restores virtual scenery to the cloud.
• In Part 9 we learn about the Azure Functions backend for the solution.

The entire project sourcecode that accompanies this series can be found at:

• GitHub : SiliconOrchid : Unity-AR-AzureSpatialAnchor-Demo

In this article, we’ll be looking at how we go about saving and retrieving the layout of the “scenery” objects using cloud storage.

This will enable us to:

• return to the same physical location at a later time and restore the same layout
• enable other people, using their own mobile devices, to share the same experience at the same time.

Applicable code in this article:

• Assets/Scripts/Managers/SceneryPersistenceManager.cs
  • View in GitHub
• Assets/Scripts/Models/SceneryItemContainerDTO.cs
  • View in GitHub
• Assets/Scripts/Models/SceneryItemDTO.cs
  • View in GitHub
• Assets/Scripts/Models/TransformComponentDTO.cs
  • View in GitHub
• Assets/Scripts/Models/SceneryUtil.cs
  • View in GitHub

Saving scenery

• The entry point to this part of the code is through the method SaveScenery() in the SceneryPersistenceManager Component.
  • This method is called by the UI “Save Scenery” button - we can find the code for that the UIManager Component, in UIButton_SaveScenery_Click().

An overview of the process that saves “scenery” objects to cloud storage is:

• the user taps the UI “Save Scenery” button
• code in SaveScenery():
  • creates a DTO object that will be used as part of the string-serialisation process.
    • the overall DTO comprises a “container” object which has a list of multiple “items”.
      
    • each “item” in DTO essentially represents the Pose of an individual “scenery” object, using a selection of float arrays.
• code in MapSceneryGameobjectsToDTO():
  • iterates over the “scenery” GameObjects in Unity, which are children of the container GameObject SpatialAnchorGroup/SceneryContainer
  • populates DTO items with information such as the sceneryTypeEnum which is used to determine whether the scenery is, for example, an “oak-tree” or a “poplar tree”.
• TransformComponentDTO class is used to:
  • model the Pose data
    
  • provides a constructor which extracts Pose data from the Transform of each object of “scenery”
• the DTO is serialised to JSON using the built-in Unity JsonUtility library.
• the Unity Coroutine method PostSceneryDataJsonToApi() is used to make an HTTP POST to our own API.
  • we specify the Url to our API in the Unity Editor, in the “GeneralConfiguration/apiUrl_SceneData” field.

Note: We’ll look at the Azure Functions backend part of this project in the final article of this series: Part 9 - Cloud Backend

Gotcha: If you are adapting this project and decide to create your own DTO classes, do not create fields that include a {get; set;} because the Unity JsonUtility does not like them and will break!

Restoring scenery

• The entry point to this part of the code is through the method RestoreScenery() in the SceneryPersistenceManager Component.
  • This method is called by the UI “Restore Scenery” button - we can find the code for that the UIManager Component, in UIButton_esScenery_Click().

An overview of the process that saves “scenery” objects to cloud storage is:

• the user taps the UI “Restore Scenery” button
• the Unity Coroutine method GetSceneryDataFromApi() is used to make an HTTP GET to our own API - a JSON result is returned.
• the byte array response from the API is mapped into the SceneryItemContainerDTO DTO object.
• list of “scenery” items modelled in the DTO is iterated upon
• SpawnNewScenery() method is used to
  • spawn an appropriate new GameObject by referring to the enumeration SceneryTypeEnum
  • add it to the scene with necessary Transforms.
  • set the parent to be the anchor “SceneryContainer”

Next, in the final part of the series, we learn about the Azure Functions backend for the solution.

NEXT: Read part 9