NeRF-FF: A Plug-in Method to Mitigate Defocus Blur for Runtime Optimized Neural Radiance Fields

Neural radiance fields (NeRFs) have revolutionized novel view synthesis, leading to an unprecedented level of realism in rendered images. However, the reconstruction quality of NeRFs suffers significantly from out-of-focus regions in the input images. We propose NeRF-FF, a plug-in strategy that estimates image masks based on Focus Frustums (FFs), i.e., the visible volume in the scene space that is in-focus. NeRF-FF enables a subsequently trained NeRF model to omit out-of-focus image regions during the training process. Existing methods to mitigate the effects of defocus blurred input images often leverage dynamic ray generation. This makes them incompatible with the static ray assumptions employed by runtime-performance-optimized NeRF variants, such as Instant-NGP, leading to high training times. Our experiments show that NeRF-FF outperforms state-of-the-art approaches regarding training time by two orders of magnitude - reducing it to under 1 min on end-consumer hardware - while maintaining comparable visual quality.