After picking up a used copy of Elemental Magic, I tried a first go at a surface bubble. This was done straight-ahead in Pencil and it’s kinda-sorta-okay for a first try, I guess. For one thing, I realized during the process just how little I know about what happens inside the bubble. And, in spite of my best efforts to make things overlap, all of the drops seem to hit at the same time. Lesson: 1 or 2 frames is not enough space to give a sense of overlap. One other problem is that, since I haven’t done much straight-ahead animation, my hang time on the droplets really sucks.
For a look at somebody who knows what he’s doing, check out this lava bubble by the author of Elemental Magic.