# inverse transform

Hi all,

Given two coordinate frames, A and B, I need to use both transforms that go between them for a given timestamp. (These two are obviously inverses of each other.) I could obviously do a lookupTransform for both separately, but that feels suboptimal.

I have been stumbling around geometric_msgs::Transform, tf2::Transform, stamped versions etc, but its a bit of a mess.

Any advice would be appreciated.

Your question is not very clear. Are the coordinate frames static? Why is using tf2 Transform sub-optimal?

Yeah, sorry about that.

It's dynamic, otherwise I wouldn't worry about efficiency.

I _think_ that lookupTransform has to do some interpolation on time and perhaps not a trivial one, hence my feeling that it is not fast. (But I might be wrong.) I thought a taking simple inverse of such a small matrix would be quicker. (Which I guess I can also write myself, but I expected to be part of tf/tf2.)

I hope this makes sense.