Как нарисовать линию / полилинию на плоскости с помощью ARCore

В разделе кода, где вы захватываете якорь, чтобы разместить объект, вы должны проверить, есть ли у вас уже предыдущий якорь. Если у вас есть предыдущая привязка, возьмите worldPosition (как объект Vector3) из предыдущих и текущих привязок, затем вычислите разницу между ними, создайте линию такой длины и прикрепите ее к сцене в средней точке между двумя точки. Наконец, установите previousAnchor на текущий.

Вот код, который я использовал для решения этой проблемы:

// Create the Anchor.
Anchor anchor = hitResult.createAnchor();
AnchorNode anchorNode = new AnchorNode(anchor);

// Code to insert object probably happens here

if (lastAnchorNode != null) {
    Vector3 point1, point2;
    point1 = lastAnchorNode.getWorldPosition();
    point2 = anchorNode.getWorldPosition();
    Node line = new Node();

    /* First, find the vector extending between the two points and define a look rotation in terms of this
        Vector. */

    final Vector3 difference = Vector3.subtract(point1, point2);
    final Vector3 directionFromTopToBottom = difference.normalized();
    final Quaternion rotationFromAToB =
          Quaternion.lookRotation(directionFromTopToBottom, Vector3.up());

    final Renderable[] lineRenderable = new Renderable[1];

    /* Then, create a rectangular prism, using ShapeFactory.makeCube() and use the difference vector
       to extend to the necessary length.  */

    MaterialFactory.makeOpaqueWithColor(this, color)
          .thenAccept(
                  material -> {
                      lineRenderable[0] = ShapeFactory.makeCube(new Vector3(.01f, .01f, difference.length()),
                              Vector3.zero(), material);
              });

    /* Last, set the world rotation of the node to the rotation calculated earlier and set the world position to
       the midpoint between the given points . */
    line.setParent(anchorNode);
    line.setRenderable(lineRenderable[0]);
    line.setWorldPosition(Vector3.add(point1, point2).scaled(.5f));
    line.setWorldRotation(rotationFromAToB);
}

lastAnchorNode = anchorNode;

Anchor будет вам полезен. благодаря этому вы можете отслеживать точки касания и использовать эти координаты между точками. Я сделал что-то подобное, чтобы подсчитать расстояние между двумя точками, которые я коснулся

Решение от @Arthulia у меня не работает = (

Но я поступил немного иначе. Оно работает:

в моем onCreate:

ArFragment arFragment = (ArFragment) getSupportFragmentManager().findFragmentById(R.id.vr_fragment);
arFragment.setOnTapArPlaneListener(
                (HitResult hitResult, Plane plane, MotionEvent motionEvent) -> {
                    addLineBetweenHits(hitResult, plane, motionEvent);
                });

и позже:

private void addLineBetweenHits(HitResult hitResult, Plane plane, MotionEvent motionEvent) {
        Anchor anchor = hitResult.createAnchor();
        AnchorNode anchorNode = new AnchorNode(anchor);

        if (lastAnchorNode != null) {
            anchorNode.setParent(arFragment.getArSceneView().getScene());
            Vector3 point1, point2;
            point1 = lastAnchorNode.getWorldPosition();
            point2 = anchorNode.getWorldPosition();

        /*
            First, find the vector extending between the two points and define a look rotation
            in terms of this Vector.
        */
            final Vector3 difference = Vector3.subtract(point1, point2);
            final Vector3 directionFromTopToBottom = difference.normalized();
            final Quaternion rotationFromAToB =
                    Quaternion.lookRotation(directionFromTopToBottom, Vector3.up());
            MaterialFactory.makeOpaqueWithColor(getApplicationContext(), color)
                    .thenAccept(
                            material -> {
/* Then, create a rectangular prism, using ShapeFactory.makeCube() and use the difference vector
       to extend to the necessary length.  */
                                ModelRenderable model = ShapeFactory.makeCube(
                                        new Vector3(.01f, .01f, difference.length()),
                                        Vector3.zero(), material);
/* Last, set the world rotation of the node to the rotation calculated earlier and set the world position to
       the midpoint between the given points . */
                                Node node = new Node();
                                node.setParent(anchorNode);
                                node.setRenderable(model);
                                node.setWorldPosition(Vector3.add(point1, point2).scaled(.5f));
                                node.setWorldRotation(rotationFromAToB);
                            }
                    );
        lastAnchorNode = anchorNode;
    }

1. Я думаю, что вам следует сохранить всю информацию HitResults, особенно для позиции Pose.

2. Вы должны создать класс как PlaneRenderer, чтобы он мог рисовать линию между начальной и конечной позицией.

using System;

namespace GoogleARCore.Examples.HelloAR
{
    using System.Collections.Generic;
    using GoogleARCore;
    using GoogleARCore.Examples.Common;
    using UnityEngine;

    #if UNITY_EDITOR
    // Set up touch input propagation while using Instant Preview in the editor.
    using Input = InstantPreviewInput;
    #endif

    /// <summary>
    /// Controls the HelloAR example.
    /// </summary>
    public class HelloARController : MonoBehaviour
    {
        /// <summary>
        /// The first-person camera being used to render the passthrough camera image (i.e. AR background).
        /// </summary>
        public Camera FirstPersonCamera;

        /// <summary>
        /// A prefab for tracking and visualizing detected planes.
        /// </summary>
        public GameObject DetectedPlanePrefab;

        /// <summary>
        /// A model to place when a raycast from a user touch hits a plane.
        /// </summary>
        public GameObject AndyPlanePrefab;

        /// <summary>
        /// A model to place when a raycast from a user touch hits a feature point.
        /// </summary>
        public GameObject AndyPointPrefab;

        /// <summary>
        /// A gameobject parenting UI for displaying the "searching for planes" snackbar.
        /// </summary>
        public GameObject SearchingForPlaneUI;

        /// <summary>
        /// The rotation in degrees need to apply to model when the Andy model is placed.
        /// </summary>
        private const float k_ModelRotation = 180.0f;

        /// <summary>
        /// A list to hold all planes ARCore is tracking in the current frame. This object is used across
        /// the application to avoid per-frame allocations.
        /// </summary>
        private List<DetectedPlane> m_AllPlanes = new List<DetectedPlane> ();

        /// <summary>
        /// True if the app is in the process of quitting due to an ARCore connection error, otherwise false.
        /// </summary>
        private bool m_IsQuitting = false;

        private int count = 0;
        private Vector3[] pos = new Vector3[4];
        private LineRenderer lineRenderer;

        /// <summary>
        /// The Unity Update() method.
        /// </summary>
        public void Update ()
        {
            _UpdateApplicationLifecycle ();

            // Hide snackbar when currently tracking at least one plane.
            Session.GetTrackables<DetectedPlane> (m_AllPlanes);
            bool showSearchingUI = true;
            for (int i = 0; i < m_AllPlanes.Count; i++) {
                if (m_AllPlanes [i].TrackingState == TrackingState.Tracking) {
                    showSearchingUI = false;
                    break;
                }
            }

            SearchingForPlaneUI.SetActive (showSearchingUI);

            // If the player has not touched the screen, we are done with this update.
            Touch touch;
            if (Input.touchCount < 1 || (touch = Input.GetTouch (0)).phase != TouchPhase.Began) {
                return;
            }

            // Raycast against the location the player touched to search for planes.
            TrackableHit hit;
            TrackableHitFlags raycastFilter = TrackableHitFlags.PlaneWithinPolygon |
                                                       TrackableHitFlags.FeaturePointWithSurfaceNormal;

            if (Frame.Raycast (touch.position.x, touch.position.y, raycastFilter, out hit)) {
                // Use hit pose and camera pose to check if hittest is from the
                // back of the plane, if it is, no need to create the anchor.
                if ((hit.Trackable is DetectedPlane) &&
                                Vector3.Dot (FirstPersonCamera.transform.position - hit.Pose.position,
                                    hit.Pose.rotation * Vector3.up) < 0) {
                    Debug.Log ("Hit at back of the current DetectedPlane");
                } else {
                    // Choose the Andy model for the Trackable that got hit.
                    GameObject prefab;
                    if (hit.Trackable is FeaturePoint) {
                        prefab = AndyPointPrefab;
                    } else {
                        prefab = AndyPlanePrefab;
                    }

                    if (count < 2) {
                        pos [count] = hit.Pose.position;
                        // Instantiate Andy model at the hit pose.
                        var andyObject = Instantiate (prefab, hit.Pose.position, hit.Pose.rotation);

                        // Compensate for the hitPose rotation facing away from the raycast (i.e. camera).
                        andyObject.transform.Rotate (0, k_ModelRotation, 0, Space.Self);

                        // Create an anchor to allow ARCore to track the hitpoint as understanding of the physical
                        // world evolves.
                        var anchor = hit.Trackable.CreateAnchor (hit.Pose);

                        // Make Andy model a child of the anchor.
                        andyObject.transform.parent = anchor.transform;
                        count++;
                    }

// Рисование линий из точек касания с помощью средства рендеринга линий

                  if (count == 2) {

                        //Creating lineRenderer object
                      lineRenderer = new GameObject("Line").AddComponent<LineRenderer>();
                      lineRenderer.startColor = Color.black;
                      lineRenderer.endColor = Color.black;
                      lineRenderer.startWidth = 0.01f;
                      lineRenderer.endWidth = 0.01f;
                      lineRenderer.positionCount = 2;
                      lineRenderer.useWorldSpace = true;    

                      //Drawing line from first touched point to the second one
                      lineRenderer.SetPosition(0,pos[0]);
                      lineRenderer.SetPosition(1,pos[1]);

                  }

                }
            }
        }

        /// <summary>
        /// Check and update the application lifecycle.
        /// </summary>
        private void _UpdateApplicationLifecycle ()
        {
            // Exit the app when the 'back' button is pressed.
            if (Input.GetKey (KeyCode.Escape)) {
                Application.Quit ();
            }

            // Only allow the screen to sleep when not tracking.
            if (Session.Status != SessionStatus.Tracking) {
                const int lostTrackingSleepTimeout = 15;
                Screen.sleepTimeout = lostTrackingSleepTimeout;
            } else {
                Screen.sleepTimeout = SleepTimeout.NeverSleep;
            }

            if (m_IsQuitting) {
                return;
            }

            // Quit if ARCore was unable to connect and give Unity some time for the toast to appear.
            if (Session.Status == SessionStatus.ErrorPermissionNotGranted) {
                _ShowAndroidToastMessage ("Camera permission is needed to run this application.");
                m_IsQuitting = true;
                Invoke ("_DoQuit", 0.5f);
            } else if (Session.Status.IsError ()) {
                _ShowAndroidToastMessage ("ARCore encountered a problem connecting.  Please start the app again.");
                m_IsQuitting = true;
                Invoke ("_DoQuit", 0.5f);
            }
        }

        /// <summary>
        /// Actually quit the application.
        /// </summary>
        private void _DoQuit ()
        {
            Application.Quit ();
        }

        /// <summary>
        /// Show an Android toast message.
        /// </summary>
        /// <param name="message">Message string to show in the toast.</param>
        private void _ShowAndroidToastMessage (string message)
        {
            AndroidJavaClass unityPlayer = new AndroidJavaClass ("com.unity3d.player.UnityPlayer");
            AndroidJavaObject unityActivity = unityPlayer.GetStatic<AndroidJavaObject> ("currentActivity");

            if (unityActivity != null) {
                AndroidJavaClass toastClass = new AndroidJavaClass ("android.widget.Toast");
                unityActivity.Call ("runOnUiThread", new AndroidJavaRunnable (() => {
                    AndroidJavaObject toastObject = toastClass.CallStatic<AndroidJavaObject> ("makeText", unityActivity,
                                                                       message, 0);
                    toastObject.Call ("show");
                }));
            }
        }
    }
}