  The task of novel view synthesis aims to generate unseen perspectives of an
object or scene from a limited set of input images. Nevertheless, synthesizing
novel views from a single image still remains a significant challenge in the
realm of computer vision. Previous approaches tackle this problem by adopting
mesh prediction, multi-plain image construction, or more advanced techniques
such as neural radiance fields. Recently, a pre-trained diffusion model that is
specifically designed for 2D image synthesis has demonstrated its capability in
producing photorealistic novel views, if sufficiently optimized on a 3D
finetuning task. Although the fidelity and generalizability are greatly
improved, training such a powerful diffusion model requires a vast volume of
training data and model parameters, resulting in a notoriously long time and
high computational costs. To tackle this issue, we propose Efficient-3DiM, a
simple but effective framework to learn a single-image novel-view synthesizer.
Motivated by our in-depth analysis of the inference process of diffusion
models, we propose several pragmatic strategies to reduce the training overhead
to a manageable scale, including a crafted timestep sampling strategy, a
superior 3D feature extractor, and an enhanced training scheme. When combined,
our framework is able to reduce the total training time from 10 days to less
than 1 day, significantly accelerating the training process under the same
computational platform (one instance with 8 Nvidia A100 GPUs). Comprehensive
experiments are conducted to demonstrate the efficiency and generalizability of
our proposed method.
