I have a 3D render of a undulating ribbon - imagine a slowly pulsing sine wave from right to left - which has various width changes throughout. I want to be able to attach a null's y-position to the ribbon, but be able to animate the x-position via keyframes.
My first thought was to quickly rotoscope an animated mask/path (so it follows the ribbon wave), and attach the null to the mask, but I'm not sure if this can be done. Or can it?
As I move the null in the x-axis, I want it to automatically parent to the pulsating ribbon in the y-axis, so I don't think tracking it will work, since that is based on a series of x-y points.
Then I thought about using an expression. Can something like sampleImage() be used to attach the y-position of the null to the ribbon, reading the embedded alpha channel of the render, so it animates and flows with the crests and troughs of the wave? Or is there another expression that could be applied?
Thanks for any help,