Use pose frames

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Issue #66 new
Nate Koenig created an issue

We should start using frames of reference when specifying poses. Something like:

<link>
<pose frame="parent_link">x y z r p y</pose>
</link>

Comments (11)

  1. Steve Peters

    Is this simply a label applied to a frame? Or does this change how the pose is interpreted? Currently all poses are offsets from the parent.

  2. Steve Peters

    What's the motivation for this? It sounds more powerful, but I'm concerned that it may be much more complex.

  3. Steve Peters

    That's a good point; it's harder to do link chains in sdf than in urdf. I think my comments are mainly concerned about making sure we get the implementation details right. Design document? I can help discuss the design.

  4. Eric Cousineau

    Added some questions about design / intent: #200

    (Marked it as an enhancement, b/c I think the action item here could just be an update to unittests to show valid usages?)

  5. Alejandro Castro

    In Drake we actually played with a very simple prototype to do exactly this. You can refer for instance to the example test sdf_parser_test.cc. In particular, I think it'd be useful to generally be able to do GetPose() as done in this example. That is, requesting a pose in general requires you specifying two frames A and B in order to get pose X_AB of frame B in frame A (sorry, I am using the monogram notation we widely adopted in Drake, docs here)

    This little prototype uses this FrameCache in order to take care of the proper chained transformations take place. It is not complete though, I believe special care must be taken for kinematic loops unintentionally created by a user, but it'd be a start.

  6. Alejandro Castro

    And I think this feature would allow clearing up the misunderstandings with conventions when specifying <frame>s and <pose>s.

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