I struggled to understand interpAccel and related functions until I read this mini-tutorial by @eradicator09
My beating heart face uses those functions for hand wake up when transitioning from dim to active (part of what you are looking for) as well as to implement the beating heart in the centre.
(just ignore the crude graphics for hands and heart used on the face looks fine to me on a small watch screen, not so good on a larger higher resolution screen.)