ARPin Local Storage Quick Start

This Quick Start guide will walk you through how to set a fixed real-world location in AR to which you can attach virtual content in Unreal. In this example, we will use the HoloLens as our platform.

By following this guide, you will know how to:

• Save ARPins locally on device.

• Delete local ARPins.

• Load local ARPins.

Step 1 - Adding and Saving ARPins

Follow these steps to spawn a virtual object in 3D space and save its data with ARPin. First, you need to set up the SpawnActor Function and then connect it to a Pin Component to pin the object to a specific location.

This guide uses the location of the user's hand provided by the HoloLens platform as the spawn locationTo be able to access the Motion Controller information on HoloLens, follow these steps:

1. Add the component Motion Controller to ARPawn in the Blueprint Editor.

2. In the Details panel, set the Motion Source to the Right hand in order to match the hand that's placing the pins.

Setting Up the Spawn Actor Function

Follow these steps to set up the Spawn Actor function. This section uses a custom Blueprint Actor called Pin Object for the virtual content.

1. Double-click the project's Pawn to open it in the Blueprint Editor.

2. Add the following functions by right-clicking in the Event Graph tab of the Blueprint Editor and searching for the names:

   • Is ARPin Local Store Supported

   • Is ARPin Local Store Ready

3. Use the boolean return values from the two functions as input to an AND logic node. Connect the result of the AND node to a Branch node. This setup makes sure both scenarios are true before executing any ARPin functions.

4. From the Branch node, add the SpawnActor from Class function. Then, set the node's Class parameter to Pin Object.

5. Add a Make Transform function to specify the local transform where the object will be spawned relative to the spawn position. Keep the default values for the local space because the world transform will be specified later.

   For details on how to add input actions to your project, see Input for general input actions.

Adding the Pin Component

Follow these steps to pin the object that was spawned in the previous section. The SpawnActor from Class function returns an Object. However, the Pin Component function expects a Scene Component. In order to pin the object, grab the object's RootComponentRootComponent, which is a Scene Component that defines the object's transformation.

1. Add the function Pin Component.

2. Drag the Return Value pin from the SpawnActor node and select Get Root Component.

3. Right-click in the Event Graph and search for the variable that holds the location where you want to pin the object. In order to spawn where your hand is on HoloLens, search for Get Motion Controller. Add it to the graph.

4. Pass the variable in as a Target to the function GetWorldTransform. Then, pass the Return Value of the function to the Pin to World Transform input of the Pin Component node. The world transform defines the world space location the component pins to.

5. Add the function Save ARPin to Local Store and pass the ARPin Object Reference, which is returned by Pin Component to the In Pin input for the Save ARPin to Local Store node. Make sure each pin has a unique save name. Then, convert the world transform to a String to set the save name.

6. Run the app on your AR device. When you perform the Select (R ) action, the pin object appears and the ARPin Local Store adds an entry for the ARPin.

Step 2 - Removing ARPins

Follow the steps below to remove ARPins from the local storage and destroy the virtual content associated with them.

1. Call Get All Pins and add a For Each Loop node to iterate through the returned array of ARPins.

2. Add the function Remove Pin to stop updating the pinned component.

3. Add the function Destroy Actor to remove the virtual pin object. Call Get Pinned Component and Get Owner to get the Actor from the ARPin and its pinned Scene Component.

4. Add the function Remove All ARPins from Local Store to remove all the saved pins from the local store after iterating through all the ARPins and destroying their pinned components.

5. Run the app on your AR device. When you perform the Select (L ) action, the pin object disappears and the ARPin Local Store removes the entry for the ARPin.

Step 3 - Loading ARPins

Follow these steps to load all ARPins saved on the device in a previous session of the app and spawn the virtual content again for the ARPins.

1. Call Load ARPins from Local Store to access all the ARPins that are saved locally on device.

2. Load ARPins from Local Store returns a map of ARPin names. In order to iterate through the items in the map, convert the map to an array by using the Values function. To access every item in the array, add a For Each Loop node.

3. In the loop body, call SpawnActor from Class with a default Make Transform function. Use the default values for the transform unless you want to offset the object from where it's going to be spawned.

4. Convert the returned object to a Scene Component with Get Root Component and pass to Pin Component to ARPin.

5. Run the app on your AR device and create a few ARPins. Restart the app and see all the pins you created previously appear in the same place when the app starts.

   To differentiate the loaded pins from newly created pins, a different material for the object was used.

Step 4 - On Your Own

In this guide, you created ARPins that are stored locally on the device. To create pins that are stored using a cloud computing service such as Azure and can be shared between multiple devices and platforms, see Microsoft's documentation for Azure Spatial Anchors in Unreal Engine.