No, not THAT kind of expression.

Here’s my first use of expressions in OpenToonz to drive animated movement using mathematical expressions.

It’s a simple set of rotations that could be easily done manually but I used it to explore how to access and setup an expression that could be used (and modified) in a few copies of the same image.  For instance, three levels of rotating fish (the same image copied twice) each with a slightly faster rotation set in the expression.

The basic expression is just:  Frame*20

That means that on frame 1 the value is 20 degrees of rotation

On frame 2 the result will be 40 degrees

On frame 3… 60 degrees

Frame 4… 80 degrees

…and when we get to frame 5o the result is… well overkill.

As soon as we hit 360 we are rotating a second time so a cyclic sequence would likely work better but again this was only a test.

With expression we could use input to drive other motion to speed up or decelerate an action or to move one object twice as fast as another.  Expressions could even be used (theoretically as I haven’t explored how deeply OpenToonz expressions go) automation of objects so that as the approach another they are either drawn in or repelled.