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How do I get the displacement vector from one object to another?

quaternion

asked 2017-08-01 12:23:40 -0600

ysl208
23 ●6 ●7 ●13

I have two objects A and B, each in the form of geometry_msgs/PoseStamped. I would like to calculate the displacement (translation & rotation) vector that I can apply to any (similar) object A' and arrive to a (similar) object B' (respectively).

I guess the vector should also be of the form PoseStamped.
For translation, can I simply take B.PoseStamped.position.x - A.PoseStamped.position.x (similar for y,z)?
For the quaternion, I am not sure if I can simply do division (since adding angles in quaternions is done by multiplication?) i.e. B.PoseStamped.quaternion.x/A.PoseStamped.quaternion.x ?

I would like to avoid having to transform the quaternion to euler and back.

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answered 2017-08-09 22:53:33 -0600

Ed Venator

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Unfortunately, you cannot do mathematical operations on the geometry_msgs message types. They are plain old ROS messages with no overloaded operators. For what you want to do, you'll need to convert the messages to tf::Pose types. Once you do that, follow the instructions in this answer to calculate displacement.

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They are plain old ROS messages [..]

+1 for this :)

That would be a PORM.

gvdhoorn ( 2017-08-10 03:24:18 -0600 )edit

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Asked: 2017-08-01 12:23:40 -0600

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