ArInstantPlacementPoint

Trackable Instant Placement point returned by ArFrame_hitTestInstantPlacement .

If ARCore has an accurate 3D pose for the ArInstantPlacementPoint returned by ArFrame_hitTestInstantPlacement it will start with tracking method AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING . Otherwise, it will start with tracking method AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE , and will transition to AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING once ARCore has an accurate 3D pose. Once the tracking method is AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING it will not revert to AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE .

When the tracking method changes from AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE in one frame to AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING in the next frame, the pose will jump from its initial location based on the provided approximate distance to a new location at an accurate distance.

This instantaneous change in pose will change the apparent scale of any objects that are anchored to the ArInstantPlacementPoint . That is, an object will suddenly appear larger or smaller than it was in the previous frame.

To avoid the visual jump due to the sudden change in apparent object scale, use the following procedure:

Keep track of the pose and tracking method of the ArInstantPlacementPoint in each frame.
Wait for the tracking method to change to AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING .
Use the pose from the previous frame and the pose in the current frame to determine the object's distance to the device in both frames.
Calculate the apparent change in scale due to the change in distance from the camera.
Adjust the scale of the object to counteract the perceived change in scale, so that visually the object does not appear to change in size.
Optionally, smoothly adjust the scale of the object back to its original value over several frames.

Summary

Enumerations

 ArInstantPlacementMode 
{
 AR_INSTANT_PLACEMENT_MODE_DISABLED 
= 0,
 AR_INSTANT_PLACEMENT_MODE_LOCAL_Y_UP 
= 2
}

enum

Used in

 ArConfig

to indicate whether Instant Placement should be enabled or disabled.

 ArInstantPlacementPointTrackingMethod 
{
 AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_NOT_TRACKING 
= 0,
 AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE 
=  
    1,
 AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING 
= 2
}

enum

Tracking methods for

 ArInstantPlacementPoint

Typedefs

 ArInstantPlacementPoint

typedef

struct ArInstantPlacementPoint_

( reference type, long-lived ).

Functions

 ArInstantPlacementPoint_getPose 
(const ArSession 
*session, const ArInstantPlacementPoint 
*instant_placement_point, ArPose 
*out_pose)

void

Returns the pose of the

 ArInstantPlacementPoint

 ArInstantPlacementPoint_getTrackingMethod 
(const ArSession 
*session, const ArInstantPlacementPoint 
*instant_placement_point, ArInstantPlacementPointTrackingMethod 
*out_tracking_method)

void

Returns the tracking method of the

 ArInstantPlacementPoint

Enumerations

ArInstantPlacementMode

ArInstantPlacementMode

Used in ArConfig to indicate whether Instant Placement should be enabled or disabled.

Default value is AR_INSTANT_PLACEMENT_MODE_DISABLED .

Properties

 AR_INSTANT_PLACEMENT_MODE_DISABLED

Instant Placement is disabled.

When Instant Placement is disabled, any ArInstantPlacementPoint that has AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE tracking method will result in tracking state becoming permanently AR_TRACKING_STATE_STOPPED .

 AR_INSTANT_PLACEMENT_MODE_LOCAL_Y_UP

Enable Instant Placement.

If the hit test is successful, ArFrame_hitTestInstantPlacement will return a single ArInstantPlacementPoint with the +Y pointing upward, against gravity. Otherwise, returns an empty result set.

This mode is currently intended to be used with hit tests against horizontal surfaces.

Hit tests may also be performed against surfaces with any orientation, however:

The resulting Instant Placement point will always have a pose with +Y pointing upward, against gravity.
No guarantees are made with respect to orientation of +X and +Z. Specifically, a hit test against a vertical surface, such as a wall, will not result in a pose that's in any way aligned to the plane of the wall, other than +Y being up, against gravity.
The ArInstantPlacementPoint 's tracking method may never become AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_FULL_TRACKING or may take a long time to reach this state. The tracking method remains AR_INSTANT_PLACEMENT_POINT_TRACKING_METHOD_SCREENSPACE_WITH_APPROXIMATE_DISTANCE . until a (tiny) horizontal plane is fitted at the point of the hit test.