Kyle Mistlin-Rude shares his fairly robust animation tool for Maya that will trace arcs on animated objects. mr_motionTrail for Maya will allow you to reposition the motion trail where it is tracked from. His example is that you could add a trail to the head of a character, but reposition the trail to track the arc of the nose. The trails update while you work adjusting the animations.
…A tool for managing motion trails and arc tracking in Maya…
Maya has always had the ability to show motion trails in the viewport, and recently has added the ability to edit them right in the viewport. However, Kyle’s mr_motionTrail goes beyond Mayas native capabilities by adding the ability move the trails around and having them retrack from their new positions, and the ability to adjust the frame ranges that the trail is drawn across.
mr_motionTrail also has a spacing marker option which will create visual markers pinpointing the position of an object on a frame by frame basis, even if the object being tracked is inheriting motion from another object in the scene – (for instance, tracking a wrist that inherits motion from the body and upper arm).
You can easily manage the trails being displayed by using the list in the tools interface where you can select, edit, or remove trails or force trails to update in one handy place.
You can see an example of the mr_motionTrail script in use to get a better idea of how useful it is at around 2:45 mark of this video:
