g
that the interpolation has not started, returning <code>a</code> (or something
equivalent to <code>a</code>), 1.0 meaning that the interpolation has finished,
returning <code>b</code> (or something equivalent to <code>b</code>), and values in between
meaning that the interpolation is at the relevant point on the timeline
between <code>a</code> and <code>b</code>. The interpolation can be extrapolated beyond 0.0 and
1.0, so negative values and values greater than 1.0 are valid (and can
easily be generated 