So I imagined it, and I came to the conclusion it's not more than a QR code.

From what I understand (which is limited) a QR code can function as a fiducial but the cutting edge of fiducials far exceed QR codes in terms of recognition speed and can be understood in terms of their relative 3D orientation to the scanner much more accurately and efficiently than QR codes.

The docs page for AprilTag[0] makes for an explanatory example,

"AprilTags are conceptually similar to QR Codes, in that they are a type of two-dimensional bar code. However, they are designed to encode far smaller data payloads (between 4 and 12 bits), allowing them to be detected more robustly and from longer ranges. Further, they are designed for high localization accuracy— you can compute the precise 3D position of the AprilTag with respect to the camera."

[0]https://april.eecs.umich.edu/software/apriltag

Something with the recognition speed and 3D orientation understanding of an AprilTag and with the information density of a QR code seems like it could be quite a useful innovation.

QR code’s are a form of fiducial markers. However, detection is far different than orientation. Also for things like AR, you need quicker detection and orientation, which QR code’s don’t afford

Yup. And Actually, you need to know the corners of the QR code pretty precisely to actually de-skew the QR tag to pull out the code from it, and it’s an easy transformation to get 6dof orientation and translation from that (although you need some idea about the camera optics, but that’s easy to calibrate with similar techniques beforehand). You’re right about about speed, though, and some fiducials are much more resistant to motion blur than QR codes are (and work with much lower resolution cameras).

Yes, I too thought this, how does a QR code not already accomplish this need?

A QR code IS a type of fiducial.

There’s an entire spectrum of fiducial types based on 2D bar code matrices. QR code is the most well known.

But 2D matrices are not as resistant to motion blur, so there are advantages to some of the other types.

You're not going to be able to encode that much data on a little stamp. Its way more reliable to use a WebVR link.

3 kilobytes (what you can store on a little fiducial QR code stamp) is a pretty large amount of data. But you don't need that much. If you just encode a 64bit identifier plus 48 bits of data encoding a bounding box in half-precision floating point for a total of 112 bits (14 bytes). Or maybe 1 byte of precision in each dimension and about 100 points defining the shape for a total of 300 bytes (and another 8 for identification).

You really can store plenty of info in a fiducial. And you can use multiple fiducials to store more if you like. This is still a pretty rich vein to mine.

I haven't seen any formats that give you that much space in a reliable way, but even then, you won't get any texture mapping, normal mapping, animation, etc etc. Why bother when you can reliably store a link and have anything you want?

Links have implied costs far greater than a few KB.

Color is tricky because it varies way too much depending on the lighting conditions, right?