  We study the problem of synthesizing a long-term dynamic video from only a
single image. This is challenging since it requires consistent visual content
movements given large camera motions. Existing methods either hallucinate
inconsistent perpetual views or struggle with long camera trajectories. To
address these issues, it is essential to estimate the underlying 4D (including
3D geometry and scene motion) and fill in the occluded regions. To this end, we
present Make-It-4D, a novel method that can generate a consistent long-term
dynamic video from a single image. On the one hand, we utilize layered depth
images (LDIs) to represent a scene, and they are then unprojected to form a
feature point cloud. To animate the visual content, the feature point cloud is
displaced based on the scene flow derived from motion estimation and the
corresponding camera pose. Such 4D representation enables our method to
maintain the global consistency of the generated dynamic video. On the other
hand, we fill in the occluded regions by using a pretrained diffusion model to
inpaint and outpaint the input image. This enables our method to work under
large camera motions. Benefiting from our design, our method can be
training-free which saves a significant amount of training time. Experimental
results demonstrate the effectiveness of our approach, which showcases
compelling rendering results.
