Lee, Shin - General Construction of Time-Domain Filters for Orientation
Data

Lee and Shin's paper discusses a method for applying a filter mask to
orientation data.  The problem they attempt to solve is finding a way to
generalize a particular manipulation of an object's positional data over a
time-lapse rotation.  This allows for such effects as smoothing or
sharpening of movement over a given rotation.  This is accomplished by
converting the orientation data of an object into their analogues in a
vector space.  Once in this form, a filter mask can then be applied, and
then converted back into orientation data.  The important properties of this
scheme are that it is a time-domain filter and satisfies
coordinate-invariance, time-invariance, and symmetry.  The mathematical
formulations are the most difficult aspect of this paper to understand.
Although the paper does a good job explaining why their method works, it is
not immediately clear from their mathematical notation.  Having a better
background in the type of space transformations they are using would be
beneficial.