Pose addition and subtraction needs work [gazebo issue 216]

[osrf-migration]

Original report (archived issue) by Louise Poubel (Bitbucket: chapulina, GitHub: chapulina).

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Moving Gazebo issue 216 here now that gazebo::math has been fully deprecated. Please consider the discussion on that issue:

https://bitbucket.org/osrf/gazebo/issues/216/pose-addition-and-subtraction-needs-work

[osrf-migration]

Original comment by Addisu Z. Taddese (Bitbucket: azeey, GitHub: azeey).

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I'm in favor of switching the semantics of operator* and removing operator+. Should we consider doing this on the gz11 branch? I think the current semantics is very counter-intuitive.

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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I think we can make that switch. There might be repercussions in our code that are difficult to debug. If you do make this switch, then you might want to make sure all Ignition libraries pass CI.

[osrf-migration]

Original comment by Michael Grey (Bitbucket: mxgrey, GitHub: mxgrey).

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We currently don't use operator* anywhere in code or in testing, because it's so confusing that it only creates errors. Instead people will usually convert Pose objects to Matrix4 objects and use the Matrix4::operator*.

I fully agree with removing operator+, although I think that operator does get used in some places in the code, so those uses will need to be replaced with the fixed version of operator*.

[osrf-migration]

Original comment by Louise Poubel (Bitbucket: chapulina, GitHub: chapulina).

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+1

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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Yeah, it's really confusing that the Pose3::operator* has an opposite sign convention to Matrix4 multiplication. I've illustrated this in an added test in 3ff1a21

• https://osrf-migration.github.io/ignition-gh-pages/#!/ignitionrobotics/ign-math/commits/7f7ed51 (3ff1a21)#Lsrc/Matrix4_TEST.ccT137

[traversaro]

I think this has been fixed (unfortunately with breaking change in the behavior of operator*(Pose3d, Pose3d) in ignition-math5/ignition-math6 with PR https://osrf-migration.github.io/ignition-gh-pages/#!/ignitionrobotics/ign-math/pull-requests/301 right? See https://github.com/ignitionrobotics/ign-math/blob/master/Changelog.md#ignition-math-620 and https://github.com/ignitionrobotics/ign-math/blob/master/Changelog.md#ignition-math-510-2019-09-11 .

[chapulina]

I think there's still the question of whether we want to remove the addition and subtraction operators:

https://github.com/ignitionrobotics/ign-math/blob/6a3c4a32b18e6bd7956fecfe53ccfe14bfcd2907/include/ignition/math/Pose3.hh#L183-L189

[scpeters]

yeah, I would support deprecating them to encourage the use of *

[traversaro]

yeah, I would support deprecating them to encourage the use of *

I personally agree. + is often used to refer to commutative operations, and using it for a non-commutative operation is quite confusing.

[scpeters]

I'll open a pull request to deprecate the + and - operators for ign-math7 and see how much trouble it causes

[scpeters]

Pose + and - operators are now deprecated in math7