Motion interpolation in Lie subgroups and symmetric subspaces

We show that a map defined by Pfurner, Schrocker and Husty, mapping points in 7-dimensional projective space to the Study quadric, is equivalent to the composition of an extended inverse Cayley map with the direct Cayley map, where the Cayley map in question is associated to the adjoint representation of the group SE(3). We also verify that subgroups and symmetric subspaces of SE(3) lie on linear spaces in dual quaternion representation of the group. These two ideas are combined with the observation that the Pfurner-Schrocker-Husty map preserves these linear subspaces. This means that the interpolation method proposed by Pfurner et al. can be restricted to subgroups and symmetric subspaces of SE(3).