Guide du développeur sur l'emplacement instantané pour Android

Découvrez comment utiliser l'API Instant Placement dans vos propres applications.

Conditions préalables

Assurez-vous de bien comprendre les concepts fondamentaux de la RA et de configurer une session ARCore avant de continuer.

Configurer une nouvelle session avec Instant Placement

Dans une nouvelle session ARCore, activez le mode Emplacement instantané.

// Create the ARCore session.
public void createSession() {
  session = new Session(applicationContext);
  Config config = new Config(session);
  // Set the Instant Placement mode.
  config.setInstantPlacementMode(InstantPlacementMode.LOCAL_Y_UP);
  session.configure(config);
}

// Create the ARCore session.
fun createSession() {
  session = Session(applicationContext);
  val config = Config(session)
  // Set the Instant Placement mode.
  config.instantPlacementMode = Config.InstantPlacementMode.LOCAL_Y_UP
  session.configure(config)
}

Placer un objet

Utilisez Frame.hitTestInstantPlacement() pour créer un point d'emplacement instantané traçable en fonction d'une position d'appui sur l'écran. Récupérez la pose actuelle avec la méthode getPose().

private placementIsDone = false;

public void onDrawFrame(GL10 gl) {
  Frame frame = session.update();

  // Place an object on tap.
  if (!placementIsDone && didUserTap()) {
    // Use estimated distance from the user's device to the real world, based
    // on expected user interaction and behavior.
    float approximateDistanceMeters = 2.0f;
    // Performs a ray cast given a screen tap position.
    List<HitResult> results =
      frame.hitTestInstantPlacement(tapX, tapY, approximateDistanceMeters);
    if (!results.isEmpty()) {
      InstantPlacementPoint point = (InstantPlacementPoint) results.get(0).getTrackable();
      // Create an Anchor from the point's pose.
      Anchor anchor = point.createAnchor(point.getPose());
      placementIsDone = true;
      disableInstantPlacement();
    }
  }
}

var placementIsDone = false;

fun onDrawFrame(gl: GL10) {
  val frame = session.update();

  // Place an object on tap.
  if (!placementIsDone && didUserTap()) {
    // Use estimated distance from the user's device to the real world, based
    // on expected user interaction and behavior.
    val approximateDistanceMeters = 2.0f;
    // Performs a ray cast given a screen tap position.
    val results = frame.hitTestInstantPlacement(tapX, tapY, approximateDistanceMeters)
    if (results.isNotEmpty()) {
      val point = results[0].trackable as InstantPlacementPoint
      // Create an Anchor from the point's pose.
      val anchor = point.createAnchor(point.pose)
      placementIsDone = true
      disableInstantPlacement()
    }
  }
}

Instant Placement est compatible avec le suivi de l'espace à l'écran avec une distance approximative, et passe automatiquement au suivi complet une fois que le point d'emplacement instantané est ancré dans le monde réel. Récupérez la pose actuelle avec getPose(). Obtenez la méthode de suivi actuelle avec getTrackingMethod().

Bien qu'ARCore puisse effectuer des tests de positionnement instantanés sur des surfaces de n'importe quelle orientation, les résultats de positionnement renvoient toujours une posture avec +Y vers le haut, contre la direction de la gravité. Sur les surfaces horizontales, les tests de positionnement renvoient les positions précises beaucoup plus rapidement.

Faciliter la transition des méthodes de suivi

Lorsque la profondeur réelle devient disponible, ARCore modifie la méthode de suivi d'un InstantPlacementPoint de SCREENSPACE_WITH_APPROXIMATE_DISTANCE à FULL_TRACKING. La position du point change également pour refléter la profondeur réelle. Cela peut donner l'impression que l'objet augmente ou rétrécit soudainement. Pour éviter ce changement soudain, ajoutez un wrapper InstantPlacementPoint.

// Wrapper class to track state to reduce sudden visual changes in object size
class WrappedInstantPlacement {
  public InstantPlacementPoint point;
  public InstantPlacementPoint.TrackingMethod previousTrackingMethod;
  public float previousDistanceToCamera;
  public float scaleFactor = 1.0f;

  public WrappedInstantPlacement(
      InstantPlacementPoint point,
      InstantPlacementPoint.TrackingMethod previousTrackingMethod,
      float previousDistanceToCamera) {
    this.point = point;
    this.previousTrackingMethod = previousTrackingMethod;
    this.previousDistanceToCamera = previousDistanceToCamera;
  }
}

// Wrapper class to track state to reduce sudden visual changes in object size
class WrappedInstantPlacement(
  var point: InstantPlacementPoint,
  var previousTrackingMethod: InstantPlacementPoint.TrackingMethod,
  var previousDistanceToCamera: Float,
  var scaleFactor: Float = 1.0f
)

Ajoutez ensuite les éléments suivants à votre activité.

List<WrappedInstantPlacement> wrappedPoints = new ArrayList<>();

public void onDrawFrame(GL10 gl) {
  Frame frame = session.update();
  Camera camera = frame.getCamera();

  // Place an object on tap.
  if (didUserTap()) {
    // Instant Placement should only be applied if no results are available through hitTest.
    List<HitResult> results = frame.hitTest(tapX, tapY);
    if (results.isEmpty()) {
      // Use the estimated distance from the user's device to the closest
      // available surface, based on expected user interaction and behavior.
      float approximateDistanceMeters = 2.0f;

      // Returns a single result if the hit test was successful.
      results =
          frame.hitTestInstantPlacement(tapX, tapY, approximateDistanceMeters);
      if (!results.isEmpty()) {
        // Instant placement was successful.
        InstantPlacementPoint point = (InstantPlacementPoint) results.get(0).getTrackable();
        wrappedPoints.add(new WrappedInstantPlacement(point, point.getTrackingMethod(),
          distance(camera.getPose(), point.getPose())));
      }
    } else {
      // results contain valid hit tests which can be used directly, so instant placement is not required.
    }
  }

  for (WrappedInstantPlacement wrappedPoint : wrappedPoints) {
    InstantPlacementPoint point = wrappedPoint.point;
    if (point.getTrackingState() == TrackingState.STOPPED) {
      wrappedPoints.remove(wrappedPoint);
      continue;
    }
    if (point.getTrackingState() == TrackingState.PAUSED) {
      continue;
    }

    if (point.getTrackingMethod() == TrackingMethod.SCREENSPACE_WITH_APPROXIMATE_DISTANCE) {
       // Continue to use the estimated depth and pose. Record the distance to
       // the camera for use in the next frame if the transition to full
       // tracking happens.
       wrappedPoint.previousDistanceToCamera = distance(point.getPose(), camera.getPose());
    }
    else if (point.getTrackingMethod() == TrackingMethod.FULL_TRACKING) {
      if (wrappedPoint.previousTrackingMethod == TrackingMethod.SCREENSPACE_WITH_APPROXIMATE_DISTANCE) {
        // Change from the estimated pose to the accurate pose. Adjust the
        // object scale to counteract the apparent change due to pose jump.
        wrappedPoint.scaleFactor = distance(point.getPose(), camera.getPose()) /
            wrappedPoint.previousDistanceToCamera;
        // Apply the scale factor to the model.
        // ...
        wrappedPoint.previousTrackingMethod = TrackingMethod.FULL_TRACKING;
      }
    }
  }
}

float distance(Pose p, Pose q) {
  return Math.sqrt(Math.pow(p.tx() - q.tx(), 2) + Math.pow(p.ty() - q.ty(), 2) + Math.pow(p.tz() - q.tz(), 2));
}

var wrappedPoints = mutableListOf<WrappedInstantPlacement>()

fun onDrawFrame(gl: GL10?) {
  val frame = session.update()
  val camera = frame.camera

  // Place an object on tap.
  if (didUserTap()) {
    // Instant Placement should only be applied if no results are available through hitTest.
    var results = frame.hitTest(tapX, tapY);
    if (results.isEmpty()) {
      // Use the estimated distance from the user's device to the closest
      // available surface, based on expected user interaction and behavior.
      val approximateDistanceMeters = 2.0f;

      // Returns a single result if the hit test was successful.
      results = frame.hitTestInstantPlacement(tapX, tapY, approximateDistanceMeters);
      if (results.isNotEmpty()) {
        // Instant placement was successful.
        val point = results[0].trackable as InstantPlacementPoint
        val wrapped = WrappedInstantPlacement(point, point.trackingMethod, point.pose.distance(camera.pose))
        wrappedPoints.add(wrapped)
      }
    } else {
      // Results contain valid hit tests which can be used directly, so Instant Placement 
      // is not required.
    }
  }

  loop@ for (wrappedPoint in wrappedPoints) {
    val point = wrappedPoint.point
    when {
      point.trackingState == TrackingState.STOPPED -> {
        wrappedPoints.remove(wrappedPoint)
        continue@loop
      }
      point.trackingState == TrackingState.PAUSED -> continue@loop
      point.trackingMethod == TrackingMethod.SCREENSPACE_WITH_APPROXIMATE_DISTANCE -> {
        // Continue to use the estimated depth and pose. Record the distance to
        // the camera for use in the next frame if the transition to full
        // tracking happens.
        wrappedPoint.previousDistanceToCamera = point.pose.distance(camera.pose)
      }
      wrappedPoint.previousTrackingMethod == TrackingMethod.SCREENSPACE_WITH_APPROXIMATE_DISTANCE &&
      point.trackingMethod == TrackingMethod.FULL_TRACKING -> {
        // Change from the estimated pose to the accurate pose. Adjust the
        // object scale to counteract the apparent change due to pose jump.
        wrappedPoint.scaleFactor =
          point.pose.distance(camera.pose) / wrappedPoint.previousDistanceToCamera
        // Apply the scale factor to the model.
        // ...
        wrappedPoint.previousTrackingMethod = TrackingMethod.FULL_TRACKING
      }
    }
  }
}

fun Pose.distance(other: Pose) = sqrt(
  (tx() - other.tx()).pow(2.0f) + (ty() - other.ty()).pow(2.0f) + (tz() - other.tz()).pow(2.0f)
)

Gagnez en efficacité après avoir placé les objets

Désactivez le placement instantané lorsque l'objet est correctement placé afin d'économiser la batterie et les cycles du processeur.

void disableInstantPlacement() {
  Config config = new Config(session);
  config.setInstantPlacementMode(Config.InstantPlacementMode.DISABLED);
  session.configure(config);
}

fun disableInstantPlacement() {
  val config = Config(session)
  // Set the Instant Placement mode.
  config.instantPlacementMode = Config.InstantPlacementMode.DISABLED
  session.configure(config)
}