Placing objects in AR

This part will help you understand how to use plane detection in AR foundation to place an object on a plane and you will create an AR app that has the functionality to place an object on a detected plane with a tap.

1. Enable Plane Detection

1. Double click on the AR Session Origin object in the Hierarchy.
2. Add the AR Plane Manager component.

1. Select Horizontal in the drop-down menu for Detection Mode.
   • You might have to click Nothing first, before setting it to Horizontal.

1. The manager is now tracking horizontal planes.

2. Visualize Planes

1. Create an AR Default Plane object by right-clicking on the Hierarchy > XR > AR Default Plane.

1. Create a Folder named Prefabs in the Assets folder by right-clicking on the Assets > Create > Folder.

1. Drag and drop the AR Default Plane object into the Prefabs folder to save it as a prefab.

1. Delete the AR Default Plane object from the Hierarchy.
2. Double click on the AR Session Origin object in the Hierarchy.
3. Drag and drop the AR Default Plane prefab from the folder into the AR Plane Manager Plane Prefab field.

3. Place cube on plane

1. Double click on the AR Session Origin object in the Hierarchy.
2. Add the AR Raycast Manager component.
3. Create a Cube by right-clicking on the Hierarchy > 3D Object > Cube.

1. Create an Empty Object by right-clicking on the Hierarchy > Create Empty and rename it to Spawn Manager.
2. Create another Empty Object named Target Object.
3. Drag and drop the Cube on the Target Object in Hierarchy.
4. Double click on the Cube object in the Hierarchy.
5. Set the scale of the cube to 0.24 in all dimensions in the Inspector.
6. Set the position of the cube to be 0.12 in the Y dimension.

1. Drag and drop the Target Object into the Prefabs folder to save it as a prefab.

1. Delete the Target Object object from the Hierarchy.

1. Create a Folder named Scripts in the Assets folder by right-clicking on the Assets > Create > Folder.

2. Create a C# Script named SpawnManager in the Assets folder by right-clicking on the Assets > Create > Folder.

3. Open SpawnManager script and replace it’s content with the script below:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.XR.ARFoundation;

public class SpawnManager : MonoBehaviour
{
    [SerializeField] Camera cam;
    [SerializeField] ARRaycastManager raycastManager;
    [SerializeField] GameObject obj;

    List<ARRaycastHit> hits;
    GameObject spawnedObj;

    private void Awake()
    {
        hits = new List<ARRaycastHit>();
        spawnedObj = null;
    }

    private void Start()
    {
        if (!cam)
            cam = FindObjectOfType<Camera>();
        if (!raycastManager)
            raycastManager = FindObjectOfType<ARRaycastManager>();
    }

    private void Update()
    {
        if (Input.touchCount == 0) return;

        RaycastHit hit;

        Touch touch = Input.GetTouch(0);
        Ray ray = cam.ScreenPointToRay(touch.position);


        if (
            !EventSystem.current.IsPointerOverGameObject(touch.fingerId)
            && raycastManager.Raycast(touch.position, hits)
        )
        {
            if (
                touch.phase == TouchPhase.Began
                && !spawnedObj
                && Physics.Raycast(ray, out hit)
            )
            {
                SpawnObject(hits[0].pose.position);
            }
            else if (
                (
                    touch.phase == TouchPhase.Moved
                    || touch.phase == TouchPhase.Began
                )
                && spawnedObj
            )
            {
                spawnedObj.transform.position = hits[0].pose.position;
            }
        }
    }

    private void SpawnObject(Vector3 position)
    {
        if (spawnedObj) Destroy(spawnedObj);
        spawnedObj = Instantiate(obj, position, Quaternion.identity);
    }
}

1. Double click on the Spawn Manager object in the Hierarchy.
2. Add the SpawnManager script as a component.
3. Drag and drop the Target Object from the Prefabs folder into the Spawn Manager Obj field.

1. You can now build and run your project. Make sure to tap your screen to instantiate a cube!

 

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