Linking AR augmentations to physical space using the ArUco marker system

Following on from the earlier work with ArUco markers, rt-ispace can now associate ArUco markers with augmentations in a space. The image above shows two glTF sample models attached to two different ArUco marker codes (23 and 24 in this case). Since these models are animated, a video also seems appropriate!

The image and video were obtained using an iPad Pro running the rt-ispace app that forms the front end for the rt-ispace system. A new server, EdgeAnchor, receives the AR video stream from the iPad via the assigned EdgeAccess, detecting any ArUco markers that may be in view. The video stream also contains the iPad camera instrinsics and AR camera pose, which allows EdgeAnchor to determine a physical pose in space of the marker relative to the camera view. The marker detection results are sent back to the iPad app (via EdgeAccess) which then matches the ArUco IDs to instantiated augmentations and calculates the world space pose for the augmentation. There are some messy calculations in there but it actually works very well.

The examples shown are set up to instantiate the augmentation based on a horizontal marker. However, the augmentation configuration allows for a 6-dof offset to the marker. This means that markers can be hung on walls with augmentations either on the walls or in front of the walls, for example.

A single EdgeAnchor instance can be shared among many rt-ispace users as no state is retained between frames allowing the system to scale very nicely. Also, there is nothing specific to ArUco markers: in principle, EdgeAnchor could support multiple marker types, providing great flexibility. The only requirement is that the marker detection results in a 6-dof pose relative to the camera.

Previously, I had been resistant to the use of markers, preferring to use the spatial mapping capabilities of the user device to provide spatial lock and location of augmentations. However, there are many limitations to these systems, especially where there is very limited visual texture or depth changes to act as a natural anchor. Adding physical anchors means that augmentations can be reliably placed in very featureless spaces which is a big plus in terms of creating a pleasant user experience.

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