| ▲ | hahahaa 13 hours ago |
| Oh yeah I mean how do the phones do that. I guess it uses dead reckoning with visual cues and some machine learning. |
|
| ▲ | dmd 13 hours ago | parent | next [-] |
| "SLAM" is the term to google. |
| |
|
| ▲ | forsalebypwner 13 hours ago | parent | prev | next [-] |
| on iPhone 12 Pro Max and later (maybe only on Pros, I forget) they have a LiDAR sensor built in, allowing for impressively accurate 3D scans of objects with a free app like Scaniverse. But yeah I think AR was the intention there |
|
| ▲ | boothby 13 hours ago | parent | prev | next [-] |
| Your phone has an accelerometer, which can be integrated twice to result in slightly accurate dead reckoning; just keep accumulating 3-vectors with every time-slice. That's a helluva lot easier than visual cues. |
| |
| ▲ | addaon 13 hours ago | parent [-] | | "slightly accurate" is the correct description, though -- dead reckoning on a cell-phone-class IMU accumulates drift too quickly to keep objects anchored in space for more than seconds at a time. You need something (visual odometry, SLAM) that provides long-term stability, even if it has short-term noise or poor availability, to fuse in. | | |
| ▲ | gregsadetsky 12 hours ago | parent [-] | | When this topic comes up, I'm always happy to share this incredible lecture from many many years ago about sensor fusion and dead reckoning and how you _cannot_ integrate acceleration twice: https://www.youtube.com/watch?v=C7JQ7Rpwn2k&t=1401s
(the whole video is incredible, but this timestamp is the magical bit) | | |
| ▲ | pezezin 12 hours ago | parent | next [-] | | 12 years ago I had to write the firmware for an IMU. It took me some real effort to convince my bosses that double integration was, for all practical purposes, impossible. I wish I had known about this video back then... IMU are very useful to known your orientation though. Even an inaccurate IMU is useful to provide an initial estimate to feed vision-based algorithms. | |
| ▲ | hahahaa 3 hours ago | parent | prev [-] | | So you tend to need additional data or assumptions to constrain the double integral? |
|
|
|
|
| ▲ | aplavin 12 hours ago | parent | prev [-] |
| In my experience, on Android, it definitely relies on camera: AR doesn't work in dark room, and barely works in slightly-lit room. So it must be fusing camera + accelerometer + ... |
