AI based digital re-aging
Disney published this paper about using AI to digitally age and de-age actors in a fraction of the time it usually takes for normal frame-by-frame manual aging techniques used today.
FRAN (which stands for face re-aging network) is a neural network that was trained using a large database containing pairs of randomly generated synthetic faces at varying ages, which bypasses the need to otherwise find thousands of images of real people at different (documented) ages that depict the same facial expression, pose, lighting, and background. Using synthetically generated training data is a method that’s been utilized for things like training self-driving cars to handle situations that aren’t easily reproducible.
The age changes are then added/merge onto the face. It appears this approach fixes a lot of the issues common in this kind of approach: facial identity loss, poor resolution, and unstable results across subsequent video frames. It does have some issues with greying hair and aging very young actors, but produces results better than techniques used just a few years ago (not that the bar was very hard to beat).