adding basic scene with marker detection

AR/Assets/ExampleAssets/Scripts/AnchorCreator.cs

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+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.XR.ARFoundation;
+using UnityEngine.XR.ARSubsystems;
+
+//
+// This script allows us to create anchors with
+// a prefab attached in order to visbly discern where the anchors are created.
+// Anchors are a particular point in space that you are asking your device to track.
+//
+
+[RequireComponent(typeof(ARAnchorManager))]
+[RequireComponent(typeof(ARRaycastManager))]
+[RequireComponent(typeof(ARPlaneManager))]
+public class AnchorCreator : MonoBehaviour
+{
+    // This is the prefab that will appear every time an anchor is created.
+    [SerializeField]
+    GameObject m_AnchorPrefab;
+
+    public GameObject AnchorPrefab
+    {
+        get => m_AnchorPrefab;
+        set => m_AnchorPrefab = value;
+    }
+
+    // Removes all the anchors that have been created.
+    public void RemoveAllAnchors()
+    {
+        foreach (var anchor in m_AnchorPoints)
+        {
+            Destroy(anchor);
+        }
+        m_AnchorPoints.Clear();
+    }
+
+    // On Awake(), we obtains a reference to all the required components.
+    // The ARRaycastManager allows us to perform raycasts so that we know where to place an anchor.
+    // The ARPlaneManager detects surfaces we can place our objects on.
+    // The ARAnchorManager handles the processing of all anchors and updates their position and rotation.
+    void Awake()
+    {
+        m_RaycastManager = GetComponent<ARRaycastManager>();
+        m_AnchorManager = GetComponent<ARAnchorManager>();
+        m_PlaneManager = GetComponent<ARPlaneManager>();
+        m_AnchorPoints = new List<ARAnchor>();
+    }
+
+    void Update()
+    {
+        // If there is no tap, then simply do nothing until the next call to Update().
+        if (Input.touchCount == 0)
+            return;
+
+        var touch = Input.GetTouch(0);
+        if (touch.phase != TouchPhase.Began)
+            return;
+
+        if (m_RaycastManager.Raycast(touch.position, s_Hits, TrackableType.PlaneWithinPolygon))
+        {
+            // Raycast hits are sorted by distance, so the first one
+            // will be the closest hit.
+            var hitPose = s_Hits[0].pose;
+            var hitTrackableId = s_Hits[0].trackableId;
+            var hitPlane = m_PlaneManager.GetPlane(hitTrackableId);
+
+            // This attaches an anchor to the area on the plane corresponding to the raycast hit,
+            // and afterwards instantiates an instance of your chosen prefab at that point.
+            // This prefab instance is parented to the anchor to make sure the position of the prefab is consistent
+            // with the anchor, since an anchor attached to an ARPlane will be updated automatically by the ARAnchorManager as the ARPlane's exact position is refined.
+            var anchor = m_AnchorManager.AttachAnchor(hitPlane, hitPose);
+            Instantiate(m_AnchorPrefab, anchor.transform);
+
+            if (anchor == null)
+            {
+                Debug.Log("Error creating anchor.");
+            }
+            else
+            {
+                // Stores the anchor so that it may be removed later.
+                m_AnchorPoints.Add(anchor);
+            }
+        }
+    }
+
+    static List<ARRaycastHit> s_Hits = new List<ARRaycastHit>();
+
+    List<ARAnchor> m_AnchorPoints;
+
+    ARRaycastManager m_RaycastManager;
+
+    ARAnchorManager m_AnchorManager;
+
+    ARPlaneManager m_PlaneManager;
+}