The problem to solve here is that while this shot is certainly possible to animate by hand, the timing and movement of both the ball and each individual steps was still being worked on.
A solution was needed that would let the animator focus on animating the ball across the screen and animate the steps cascading up, without needing to manually animate the Y position of the ball.
After some experimentation, I settled on an expression-based workflow that would look at the floor & all the steps layers in the scene, and ensure the ball always sat on top.
This involved checking which layer the ball was on top of at any given moment, so that it'd respond properly to the right layer.
With this approach, the artists could set the ball animation in one place, then only worry about how and when the steps animated up– no matter what, the ball would always roll over them.
Zack Lovatt focuses on toolkitting, building custom studio pipelines, expression rigging projects, and creating data-driven animation workflows.