I'm trying to work with pairs of industrial robots that need to move to specific positions relative to each other within a given frame ofreference. To do this, I need a means to (among other things) take the 6DOF (3d location and Euler-angle orientation) position of one robot and translate it into the other robot's frame of reference. And just to frost the cake, I sometimes need to match the two robots orientation in two axes but not the third (think of two pencils held point-to-point -- their long axes must be kept parallel, but they are free to rotate *around* their long axes). I've done days and weeks of Googling, and found lots of articles on matrix algebra and converting vectors between reference frames, but nothing directly applicable to what I need. And I don't have the time, resources, or skills to derive the entire process from first principles. I figure I can't be the first person to need to do something like this, so somewhere there must be an algorithm or a set of guidelines from someone else's previous experience that I just haven't been able to find. Anyone ever see something like this?