Taming Uncertainty in Sparse-view Generalizable NeRF via Indirect Diffusion Guidance

Neural Radiance Fields (NeRF) have demonstrated effectiveness in synthesizing novel views. However, their reliance on dense inputs and scene-specific optimization has limited their broader applicability. Generalizable NeRFs (Gen-NeRF), while intended to address this, often produce blurring artifacts in unobserved regions with sparse inputs, which are full of uncertainty. In this paper, we aim to diminish the uncertainty in Gen-NeRF for plausible renderings. We assume that NeRF's inability to effectively mitigate this uncertainty stems from its inherent lack of generative capacity. Therefore, we innovatively propose an Indirect Diffusion-guided NeRF framework, termed ID-NeRF, to address this uncertainty from a generative perspective by leveraging a distilled diffusion prior as guidance. Specifically, to avoid model confusion caused by directly regularizing with inconsistent samplings as in previous methods, our approach introduces a strategy to indirectly inject the inherently missing imagination into the learned implicit function through a diffusion-guided latent space. Empirical evaluation across various benchmarks demonstrates the superior performance of our approach in handling uncertainty with sparse inputs.