Doubt on "SmartProjectionFactor" expected usage

[José Luis Blanco-Claraco]

Hi gtsam friends:

I tried to look for a complete example on how to use
SmartProjectionFactor to estimate camera poses *and* calibration
(multiple views from one single camera, so, just one calibration
unknown) but couldn't find it... pointers will be appreciated :-)

In particular, this is what I understand so far and what doesn't make
sense to me:
- SmartProjectionFactor<> instances should be added to the FG, one per
tracked landmark.
- Its constructor takes just the noise model and some params.
- For each Smart Factor instance, one must call add() once per LM observation.
- Arguments of add() are the Z (camera observation, u,v), and the
**camera key**.
- This camera key is expected to be indexing a "Value" of something
like "gtsam::PinholeCamera<gtsam::Cal3DS2>".

Here's the problem:
- Each such "PinholeCamera" variable accepts in its ctor a pose and a
calibration (by value, *not* keys).

So, how can it be enforced that all "cameras" have one single
calibration, if there's no key for a "Calibration" value? What am I
missing?

Best,
JL

PS: Yes, I shamelessly admit I have already checked with all modern
AIs and none produced examples that actually even build :-)
PS2: I already had a functional version with regular (no "smart")
factors, but I wanted to check if the latter is more robust in some
way.

--

/**
* Jose Luis Blanco-Claraco
* Universidad de Almería - Departamento de Ingeniería
* [Homepage]( https://w3.ual.es/~jlblanco/ )
* [GH profile]( https://github.com/jlblancoc )
*/

[Dellaert, Frank]

I think what you want is not possible right now :-)

You could​ use SmartProjectionFactor<Camera> and constrain the calibrations to be the same. Or, make your own factor based on SmartFactorBase :-)

PR appreciated! Although, it might be expensive, need to order calibration last :-)

Frank

Best!

Frank

---

From: 'José Luis Blanco-Claraco' via gtsam users <gtsam...@googlegroups.com>
Sent: Saturday, April 26, 2025 12:28:35 PM
To: gtsam users <gtsam...@googlegroups.com>
Subject: [GTSAM] Doubt on "SmartProjectionFactor" expected usage

 

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[José Luis Blanco-Claraco]

Thanks Frank.
At least, I feel better that it's not that I couldn't find it :-)
I'll consider the option of a new factor, if time permits (!).

Cheers,
JL