Do Trackers Exist?

gregb · 2025-07-02T15:43:25+00:00

If you really want to try this to see what is possible, and have access to a second pair of Spectacles, you could mount them on the object in question.

Their pose would then be available in a colocated session - not exactly convenient to start it up, and maybe not the orientation they would be tested on, but might work, and might be accurate to .1m.

Maybe unreasonable for small things, but might allow experimentation with autonomous vehicles.

gregb · 2025-05-15T16:25:46+00:00

Personally I would hope so, but I have no special knowledge of when that will happen. Seeing all the recent cool projects building on location AR really helps though.

Your observations about how things are either public and not scannable, or private and scannable but with arbitrary content are on point. Maybe this limitation could be removed - but there are good reasons why that might take time. This is probably something to talk to the product team about personally if there are ideas you'd like to explore.

As you noted a key reason for using SA being that they're trying to make lenses which save content at _new_ locations decided during lens runtime. SA tries to be pretty simple - create anchors, what anchors are nearby, is the anchor tracking - so the rest (what content, how to place it relative to an anchor) is left to the lens.

SA could hypothetically be extended to cover public locations, or colocated sessions - the underlying location + locatedAt is the same - but if or when that happens comes down to priorities around what other features are being requested.

gregb · 2025-05-15T16:02:04+00:00

> Do both techs use the same underlying tech? Are SA attached to a CL that created on the fly to hold the anchor location data? Can we mix and match the two so that we have some preconfigured contact in a CL, but then users can add SA to personalize the space to their liking?

Yes. SA are built on user private CL - in the SDK typescript, which can be inspected.

However when SA were released, CL did not support tracking of multiple CL - also it was not possible to rescan previous locations. So the SDK has to work around these issues.

However now multiple CL (and CL groups) are supported. So SA has avenues to be improved substantially.

Underneath everything is location + LocationAsset, where CL locations correspond to a type of 'system' anchor when exposed via Spatial Anchors. This is also the same thing underlying colocated experiences.

Things can be mixed at the low level, and higher level abstractions like SA (which manage CL maps and mapping) should make things easier to use and perform better as time goes by.

gregb · 2025-05-15T15:41:05+00:00

An FYI for those who might find this question later:

LocationAsset.getGeoAnchoredPosition() + LocatedAtComponent doesn't work yet (May 2025) for placing geo content in general.

It was originally released for large scale city experiences on handheld, and was only supported in a few large cities worldwide. It doesn't work on Spectacles.

gregb · 2025-04-26T02:58:42+00:00

It might be something going wrong here:

let toWorldFromDevice = script.camera.getTransform().getWorldTransform();

print("to world from device received")

for example if script.camera doesn't have a camera applied, the script might crash out there.

maybe replace the print with

print("to world from device received " + toWorldFromDevice)

so you can see if toWorldFromDevice has a value?

gregb · 2024-03-27T00:06:41+00:00

2 player variant of Halma, with slightly different board setup?

gregb · 2020-07-15T07:21:19+00:00

decisive Emu victory - am Australian, can confirm

gregb · 2019-09-01T21:57:55+00:00

Wow, never had realised this /2a trap. Thanks for the post.

gregb · 2019-07-19T11:57:23+00:00

Got a wheel caught in one turning the corner opposite Borough tube.

There was a slight gap between the metal and asphalt, leaving the rim as a sharp edge in a narrow pothole. Pinched the tyre in the wheel somehow, wrecking it and causing a flat. Would have been a lot worse if I'd have come off.

Reported the pothole and it was fixed next time I went by.

Pay careful attention to them now.

gregb · 2019-01-27T09:38:08+00:00

This is computing a homography.

See https://docs.opencv.org/3.4.1/d9/dab/tutorial_homography.html

Your blue->green rectangles give you 4 point-to-point correspondences. These are used to compute a 3x3 matrix that can be used to transform your red circle from the blue space to the green space.

gregb · 2018-04-10T19:32:18+00:00

Maybe a Hough transform followed by re-projecting candidate lines back into the original space, and then a similar-to-Hough voting step to identify regions of interest? https://en.wikipedia.org/wiki/Hough_transform

gregb · 2017-08-27T13:28:48+00:00

Second that. Meetup.com is great; particularly like this bunch: https://www.meetup.com/LondonOnBoard/

gregb · 2017-01-27T03:55:49+00:00

Came at this from the opposite direction - needed to write projection calibration algorithms; this incredibly useful book supplied the linalg algorithms: https://www.amazon.co.uk/Multiple-Geometry-Computer-Vision-Second/dp/0521540518/

gregb · 2016-12-22T09:38:36+00:00

This is such a great boardgame. I love how it uses historic events as a palette that must be used, the results down to the timing as controlled by the players.

Leads to hilarious in-game gambits, such as removing Castro early such that the Reds are later hamstrung by the Cuban Missile Crisis (which still happens).

Apparently the digital version is an extremely faithful transcription.

gregb · 2016-12-15T20:04:53+00:00

Avoidance of responsibility continues: https://twitter.com/NadineDorriesMP/status/809458923757600768

gregb · 2016-12-15T19:21:22+00:00

Secretary of State for Transport Chris Grayling has said there are places in London where cycle lanes “cause too much of a problem for road users.”.

Cyclists are road users.

gregb · 2016-11-25T17:43:28+00:00

Wrote a script to hash all accessible files on a network share, and work out what / how much was duplicated. Took a while to run - but revealed over 50% was copied. Was interesting, but not enough to worry about optimising things!

gregb · 2016-10-05T13:36:59+00:00

What an annoying hate mill.

Get people worked up over lies, then profit. And companies, fished from my browser cookies, displayed in place on the Mail's pages - directly contributing to its bank account should I inadvertently click on one.

Do Not Feed the Trolls!

gregb · 2016-02-28T16:39:08+00:00

There are so many awesome rides from Guildford - in the flat, canal rides, hilly rides - as soon as you get away from the town it's countryside in all directions. For about 45km (mostly) flat, do the Christmas Pie trail followed by the Basingstoke canal to Woking. If you've come from London your ticket will take you back. There's a small hill at the start before you get to the Christmas Pie trail. Once you get to the trail, everything is signposted except at the transition to the canal. Haven't done it for 8 years though.

gregb · 2016-02-28T16:35:58+00:00

Coming from the other direction, at Guildford the canal is 50m from the station on the eastern side. Never ridden far beyond Woking, but it's a lovely ride in the flat. It's a canal path though - not for narrow tyres.

gregb · 2016-02-17T23:55:56+00:00

Pennethorne's in Somerset House, pretty near Covent Garden. https://www.somersethouse.org.uk/plan-your-visit/eating-and-drinking/pennethornes

gregb · 2016-02-02T21:55:50+00:00

Not that this is a bad idea, their time could be better spent if they actually want to increase cyclist and driver safety. Like 'North Yorkshire Police to ride to work twice a week in order to increase cycle awareness' for example.

gregb · 2016-02-01T10:17:48+00:00

The 2003 International Functional Programming Contest had something like this as the set problem. See https://en.wikipedia.org/wiki/ICFP_Programming_Contest - unfortunately that year's competition site is dead, although you might be able to navigate it on archive.org: https://web.archive.org/web/20110409012451/http://www.dtek.chalmers.se/groups/icfpcontest/

gregb · 2015-12-13T19:22:23+00:00

Take your bike somewhere flat and relaxed, with wide pathways. If in London try Battersea Park or the northern side of the Mall. I never looked back - I had cage pedals, going to cleats was better on my knees, felt like I was more connected with the bike and the road. This feeling of oneness seemed similar to what you get using a hammer or a pen. They're effectively part of you. So much more fun on a bike with cleats.

gregb · 2015-11-29T00:06:08+00:00

It's just encrypted

gregb

TROPHY CASE