In some fields (graphics?) some folks like to make a strong distinction between a point and a vector, but I agree that it is redundant to have both. I would also definitely vote for combining Transform and Pose, since the message type conversions are cumbersome. It raises the question of which name to keep... I would vote Transform, since it is more general.<br>
<br>--Adam<br><br><br><br clear="all">Adam Leeper<br>Stanford University<br><a href="mailto:aleeper@stanford.edu">aleeper@stanford.edu</a><br>719.358.3804<br>
<br><br><div class="gmail_quote">On Tue, Oct 19, 2010 at 7:11 AM, Armin Hornung <span dir="ltr"><<a href="mailto:HornungA@informatik.uni-freiburg.de">HornungA@informatik.uni-freiburg.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
Alright, I changed the message title so that maybe there can be more<br>
opinions on it. If you haven't read it, see full message below for<br>
reference (which was a reply to Tully's notification of common_msgs API<br>
changes)<br>
<br>
Am 15.10.2010 13:57, schrieb Andreas Tropschug:<br>
> As I see it (which is based on, well... only me)<br>
><br>
> This inconvenience is related to geometry_msgs being<br>
> "message" types. Messages are often autogenerated types.<br>
> They are not meant to do math with, they are a serialization wrapper.<br>
><br>
> I am guessing one should convert to tf (bullet) types with the<br>
> tf::<type>MsgToTf() family of functions as soon as they are not<br>
> messages anymore, but mathematical entities.<br>
> Then all the consistencies (Poses being only typedefs of transforms for<br>
> instance) and<br>
> math operator goodies are all there.<br>
<br>
That's all correct, but that still doesn't explain why there should be<br>
both Pose[Stamped] vs. Transform[Stamped], and Point vs. Vector3<br>
messages. In fact, it only creates more confusion because now there also<br>
need to be more conversion methods to and from tf or bullet to do math.<br>
And for some navigation-related things (see the example I mentioned<br>
about Odometry), you even need to fill in *both* types of messages.<br>
<br>
If there's only a historical reason that there are both, then I feel<br>
like they should be merged for Diamondback (i.e. 22nd of October? What<br>
else needs to be done until then for that?)<br>
<br>
<br>
Best regards,<br>
Armin<br>
<br>
<br>
<br>
> Am 15.10.2010 11:02, schrieb Armin Hornung:<br>
>> Am 08.10.2010 19:51, schrieb Tully Foote:<br>
>>> If you want changes in common_msgs for diamondback please pay attention.<br>
>> I'm not sure if that's worth a review or change, or if I'm just unaware<br>
>> of some details. But I always wondered why there is a difference between<br>
>> geometry_msgs::Pose[Stamped] and Transform[Stamped]. The data fields are<br>
>> identical, the only difference I see is semantically (translation as<br>
>> "Vector3" vs position as "Point", rotation vs orientation). This makes a<br>
>> quick (& efficient) conversion between the two not possible, the single<br>
>> fields have to be copied instead (which I see myself doing quite often<br>
>> e.g. in a localization code; best example: [1]).<br>
>><br>
>> This boils down to Point vs. Translation, is there a reason to have<br>
>> both? Mathematically this is really the same (a point is just a<br>
>> translation from the origin), with only a very small semantic difference<br>
>> (which could be expressed in the variable or topic name at hand, if needed).<br>
>><br>
>> [1]<br>
>> <a href="http://www.ros.org/wiki/navigation/Tutorials/RobotSetup/Odom#Writing_the_Code" target="_blank">http://www.ros.org/wiki/navigation/Tutorials/RobotSetup/Odom#Writing_the_Code</a><br>
>><br>
>> Best regards,<br>
>> Armin<br>
><br>
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<br>
<br>
--<br>
Armin Hornung Albert-Ludwigs-Universität<br>
<a href="http://www.informatik.uni-freiburg.de/%7Ehornunga" target="_blank">www.informatik.uni-freiburg.de/~hornunga</a> Dept. of Computer Science<br>
<a href="mailto:HornungA@informatik.uni-freiburg.de">HornungA@informatik.uni-freiburg.de</a> Humanoid Robots Lab<br>
Tel.: +49 (0)761-203-8010 Georges-Köhler-Allee 79<br>
Fax : +49 (0)761-203-8007 D-79110 Freiburg, Germany<br>
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</blockquote></div><br>