Placing and Manipulating Objects in AR

Unity ID

Premium

Tutorial

Intermediate

30 Mins

Overview

Summary

In this tutorial, we’ll learn how to use the AR Session and AR Session Origin, which are part of the Unity AR Foundation package, to place and manipulate objects in AR.

Topics we'll cover

Language

English

Recommended Unity Versions

2019.1 and Above

Tutorial

Placing and Manipulating Objects in AR

Create AR Session GameObject

From the GameObject drop-down, select XR > AR Session. You won’t be interacting with the AR Session directly, but rather allows the AR world to interact with the real world.

AR Camera Orientation

Next, add an AR Session Origin. This provides the AR camera and orients the AR world in the real world. Delete the existing Main Camera in the Scene and assign the MainCamera tag to the AR Camera. (Figure 01)
 

Create Placement Indicator GameObject

When you place an object in AR, a placement indicator will tell you if you’ve selected a valid location.
To create a placement indicator, create an empty GameObject and name it Placement Indicator.

Use a Quad as the Placement Indicator

From the GameObject drop-down in the Unity Editor, select 3D Object > Quad.
Drag and drop the Quad onto Placement Indicator, making it a child of Placement Indicator.

Reset Object Transforms

In the Quad’s Inspector, zero out the position and rotate 90 degrees about the X axis. (Figure 02)
 

Identify the Placement Indicator with a Texture

Rather than a solid square, you may want to put a reticle texture on the Quad. In that case, set its material type to Unlit/Transparent and drop a reticle image into the Texture slot. (Figure 03)
 

Create a new GameObject to hold a script

Create an empty GameObject and name it Interaction.

Attach a new script to the GameObject

Attach a new C# script to Interaction, named ARTapToPlaceObject.

Create the Code

Double click ARTapToPlaceObject in the Project View to open it in your Script Editor.
Beginning on line 4, type:
usingUnityEngine.XR.ARFoundation; 
usingUnityEngine.Experimental.XR; 
usingSystem;

10.

Define Public Variables

Inside the class definition, before Start(), type:
publicGameObjectobjectToPlace;
publicGameObjectplacementIndicator;
publicCameraARCamera;

privateARSessionOriginarOrigin;
privatePoseplacementPose;
privateboolplacementPoseIsValid = false;
privateboolobjectPlaced = false;

11.

Create Start

Inside Start(), type:
arOrigin = FindObjectOfType<ARSessionOrigin>();

12.

Update

Inside Update(), type:
UpdatePlacementPose();
UpdatePlacementIndicator();
if(placementPoseIsValid && Input.touchCount > 0&& Input.GetTouch(0).phase == TouchPhase.Began && objectPlaced == false)
{
PlaceObject();
objectPlaced = true;
}

13.

Update functions

In Update(), we call a few functions that haven’t been defined yet. Let’s do that now. Create some whitespace between the Update()method and the end of the class, and type:
privatevoidPlaceObject()
{
   Instantiate(objectToPlace, placementPose.position, placementPose.rotation);
}

privatevoidUpdatePlacementIndicator()
{
   if(placementPoseIsValid && objectPlaced == false)
   {
      placementIndicator.SetActive(true);
      placementIndicator.transform.SetPositionAndRotation(placementPose.position, placementPose.rotation);
   }
   else
   {
      placementIndicator.SetActive(false);
   }
}

privatevoidUpdatePlacementPose()
{
   varscreenCenter = ARCamera.ViewportToScreenPoint(newVector3(0.5f, 0.5f));
   varhits = newList<ARRaycastHit>();
   arOrigin.Raycast(screenCenter, hits, TrackableType.Planes);
   placementPoseIsValid = hits.Count > 0;
   if(placementPoseIsValid)
   {
      placementPose = hits[0].pose;
      varcameraForward = Camera.current.transform.forward;
      varcameraBearing = newVector3(cameraForward.x, 0, cameraForward.z).normalized;
      placementPose.rotation = Quaternion.LookRotation(cameraBearing);
   }
}

14.

Save Script

The script is now complete. Save changes and return to the Unity Editor.

15.

Create an instance of the GameObject

To instantiate your Prefab, drag it into the slot marked Object To Place.

16.

Set Placement Indicator

Drag your Placement Indicator into the slot marked Placement Indicator.

17.

Set AR Camera

Drag the AR Camera into the slot marked AR Camera.
The Interaction setup is complete. (Figure 04)
 

18.

Setup Raycasting

We’re almost ready to build and test our project. We still need an EventSystem for our Raycast to work. From the GameObject drop-down, select UI > Event System.

19.

Build and Deploy 

Build and deploy your project. You should now be able to place objects in valid locations in AR, as indicated by the Placement Indicator. (Figure 05)
 

20.

Conclusion

Getting started with AR in Unity is easy, and the possibilities are endless.

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