  A sketch is one of the most intuitive and versatile tools humans use to
convey their ideas visually. An animated sketch opens another dimension to the
expression of ideas and is widely used by designers for a variety of purposes.
Animating sketches is a laborious process, requiring extensive experience and
professional design skills. In this work, we present a method that
automatically adds motion to a single-subject sketch (hence, "breathing life
into it"), merely by providing a text prompt indicating the desired motion. The
output is a short animation provided in vector representation, which can be
easily edited. Our method does not require extensive training, but instead
leverages the motion prior of a large pretrained text-to-video diffusion model
using a score-distillation loss to guide the placement of strokes. To promote
natural and smooth motion and to better preserve the sketch's appearance, we
model the learned motion through two components. The first governs small local
deformations and the second controls global affine transformations.
Surprisingly, we find that even models that struggle to generate sketch videos
on their own can still serve as a useful backbone for animating abstract
representations.
