Arcore-android-sdk: Detect closest feature point on HitTest

[smahurkar]

If I hit test using a 2D coordinate on the screen, often the HitResult list can be empty. Is it possible to return the closest point or trackable instead of an empty list?

[inio]

Your best approach is probably to iterate through the available point cloud points, compute the screen space position of each (multiply by projection_matrix * view_matrix and divide by the resulting w coordinate, then map -1..1 onto the display width and height) and find the one that's closest in screen cordinates.

[dsternfeld7]

If using Sceneform, you can use Camera.worldToScreenPoint to convert a world position into a screen position.

[smahurkar]

I am using Sceneform. I used PointCloud to get the float buffer with points, and Camera.worldToScreenPoint to find the closest Point in float buffer.

How can I create an anchor at the closest point from the float buffer? Do I need to run a HitTest from the ScreenPoint position or is there a way to use the 3D position extracted from Float buffer?

[inio]

use Session.createAnchor(Pose.makeTranslation(...)) to create an anchor at an arbitrary location.

[inio]

Closing for inactivity.

[arnsniper]

Pose.makeTranslation() only gives the position with default rotation. What if we want orientation as well? I know how to use Pose.makeRotation() but going by the way mentioned above, how can we extract the quaternion of the closest point?

[inio]

@arnsniper: Individual points don't have an orientation. It's only when you hit test agains them that we search for a planar cluster and compute a pose normal to the fit plane. If you want to combine the orientation of one pose and a separate translation you can do Pose.makeTranslation(...).compose(orientedPose.extractRotation()).