Practical Parameterization of Rotations Using the Exponential Map

This paper describes the use of exponential maps to represent rotations.
Exponential maps store rotation data using only 3 real numbers, and
therefore the representation has singularities.
The beautiful part about this paper was describing why the representation
(\theta x, \theta y, \theta z) is really bad (numerical unstabilities when
\theta is small). This is the intuition why they store sin (\theta)
instead of just \theta. (And it looks like this is why quaternions do the
same thing)

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