Angle-axis framework

Introduction

In the angle-axis framework, rotations are described by a vector of rotation, while its magnitude is the angle of rotation. A good review on rotations in general can be found here.

Another useful resource is Dwaipayan and David's PCCP paper [1]. It tells you how to write down the first and second derivatives in angle-axis framework. Note, however, that there is a mistake in the formula for R_{kl} in the limit \theta = 0. This has been corrected both in GMIN and OPTIM implementations.

Random rotations and takestep

Be carefule with random rotations and takestep in the angle axis framework. Always use the functions rot_random_* and rot_takestep_aa. For an outline of the problem see this talk.

Normal modes

Computation of normal modes in angle-axis framework: talk