unreal-uxt-ch3.md

title	description	author	ms.author	ms.date	ms.topic	ms.localizationpriority	keywords
3. Setting up your project for mixed reality	Part 3 of 6 in a tutorial series to build a simple chess app using Unreal Engine 4 and the Mixed Reality Toolkit UX Tools plugin	hferrone	v-hferrone	06/10/2020	article	high	Unreal, Unreal Engine 4, UE4, HoloLens, HoloLens 2, mixed reality, tutorial, getting started, mrtk, uxt, UX Tools, documentation, mixed reality headset, windows mixed reality headset, virtual reality headset

3. Setting up your project for mixed reality

Overview

In the previous tutorial, you spent time setting up the chess app project. This section is going to walk you through setting up the app for mixed reality development, which means adding an AR session. You'll be using an ARSessionConfig data asset for this task, which has a lot of useful AR settings like spatial mapping and occlusion. If you want to dive deeper, the Unreal Engine documentation has more details on the ARSessionConfig asset and the UARSessionConfig class.

Objectives

• Working with Unreal Engine's AR settings
• Using an ARSessionConfig data asset
• Setting up a Pawn and game mode

Adding the session asset

AR sessions in Unreal don't happen by themselves. To use a session you need an ARSessionConfig data asset to work with, which is your next task:

1. Click Add New > Miscellaneous > Data Asset in the Content Browser. Make sure you're at the root Content folder level.
   • Select ARSessionConfig, click Select, and name the asset ARSessionConfig.

3. Double-click ARSessionConfig to open it, leave all default settings and hit Save. Return to the Main window.

With that done, your next step is to make sure that the AR session starts when the level loads and stops when the level ends. Luckily, Unreal has a special kind of blueprint called a Level Blueprint that acts as a level-wide global event graph. Connecting the ARSessionConfig asset in the Level Blueprint guarantees the AR session will fire right when the game starts playing.

1. Click Blueprints > Open Level Blueprint from the editor toolbar:

5. Drag the execution node (left-facing arrow icon) off Event BeginPlay and release. Search for the Start AR Session node and hit enter.
   • Click the Select Asset dropdown under Session Config and choose the ARSessionConfig asset.

6. Right-click anywhere in the EventGraph and create a new Event EndPlay node. Drag the execution pin and release. Search for a Stop AR Session node and hit enter. If the AR session isn't stopped when the level ends, certain features may stop working if you restart your app while streaming to a headset.
   • Hit Compile, then Save and return to the Main window.

Create a Pawn

At this point, the project still needs a player object. In Unreal, a Pawn represents the user in the game, but in this case it's going to be the HoloLens 2 experience.

1. Click Add New > Blueprint Class in the Content folder and expand the All Classes section at the bottom.
   • Search for DefaultPawn, click Select, name it MRPawn, and double-click the asset to open.

Note

By default, Pawns have mesh and collision components. In most Unreal projects, Pawns are solid objects that can collide with other components. Since the Pawn and user are the same in mixed reality, you want to be able to pass through holograms without any collisions.

2. Select CollisionComponent from the Components panel and scroll down to the Collision section of the Details panel.
   • Click the Collision Presets dropdown and change the value to NoCollision.
   • Do the same for the MeshComponent

3. Click Add Component > Camera from the Components panel and name it Camera. This allows the player camera to move with the HoloLens 2 device.

Note

Make sure that the Camera component is a direct child of the root (CollisionComponent).

4. Compile and Save the Blueprint.

With your work here done, return to the Main Window.

Create a Game Mode

The last puzzle piece of the mixed reality setup is the Game Mode. The Game Mode determines a number of settings for the game or experience, including the default pawn to use.

1. Click Add New > Blueprint Class in the Content folder and expand the All Classes section at the bottom.
   • Search for Game Mode Base, name it MRGameMode and double-click to open.

2. Go to the Classes section in the Details panel and change the Default Pawn Class to MRPawn.
   • Hit Compile, then Save and return to the Main window.

3. Select Edit > Projects Settings and click Maps & Modes in the left-hand list.
   • Expand Default Modes and change Default Game Mode to MRGameMode.
   • Expand Default Maps and change both EditorStartupMap and GameDefaultMap to Main. This way when you close and reopen the editor, or play the game, the Main map will be selected by default.

With the project fully setup for mixed reality, you're ready to move on to the next tutorial and start adding user input to the scene.

Next Section: 4. Making your scene interactive