Smooth Diffusion: Crafting Smooth Latent Spaces in Diffusion Models
Authors: name: Jiayi Guo, name: Xingqian Xu, name: Yifan Pu, name: Zanlin Ni, name: Chaofei Wang, name: Manushree Vasu, name: Shiji Song, name: Gao Huang, name: Humphrey Shi

Recently, diffusion models have made remarkable progress in text-to-image
(T2I) generation, synthesizing images with high fidelity and diverse contents.
Despite this advancement, latent space smoothness within diffusion models
remains largely unexplored. Smooth latent spaces ensure that a perturbation on
an input latent corresponds to a steady change in the output image. This
property proves beneficial in downstream tasks, including image interpolation,
inversion, and editing. In this work, we expose the non-smoothness of diffusion
latent spaces by observing noticeable visual fluctuations resulting from minor
latent variations. To tackle this issue, we propose Smooth Diffusion, a new
category of diffusion models that can be simultaneously high-performing and
smooth. Specifically, we introduce Step-wise Variation Regularization to
enforce the proportion between the variations of an arbitrary input latent and
that of the output image is a constant at any diffusion training step. In
addition, we devise an interpolation standard deviation (ISTD) metric to
effectively assess the latent space smoothness of a diffusion model. Extensive
quantitative and qualitative experiments demonstrate that Smooth Diffusion
stands out as a more desirable solution not only in T2I generation but also
across various downstream tasks. Smooth Diffusion is implemented as a
plug-and-play Smooth-LoRA to work with various community models. Code is
available at https://github.com/SHI-Labs/Smooth-Diffusion.