Fast Construction of Accurate Quaternion Splines
In 1992, Barr et al proposed a method for interpolating orientations with unit quaternion curves by minimizing covariant acceleration. This paper presents a simple improved method which uses cubic basis functions to achieve a speedup of up to three orders of magnitude. A new criterion for automatic refinement based on the Euler-Lagrange error functional is also introduced.
Ravi Ramamoorthi and Alan H. Barr. "Fast Construction of Accurate Quaternion Splines". In SIGGRAPH '97, pages 287–292, 1997.