F2-NeRF: Fast Neural Radiance Field Training with Free Camera Trajectories

CVPR 2023 (highlight)

1The University of Hong Kong, 2S-Lab, Nanyang Technological University, 3Max Planck Institute for Informatics 4Texas A&M University *Equal contribution

@Shifeng Park. Trained for ~47 minutes on a single Nvidia GPU.


This paper presents a novel grid-based NeRF called F2-NeRF (Fast-Free-NeRF) for novel view synthesis, which enables arbitrary input camera trajectories and only costs a few minutes for training. Existing fast grid-based NeRF training frameworks, like Instant-NGP, Plenoxels, DVGO, or TensoRF, are mainly designed for bounded scenes and rely on space warping to handle unbounded scenes. Existing two widely-used space-warping methods are only designed for the forward-facing trajectory or the 360 degree object-centric trajectory but cannot process arbitrary trajectories. In this paper, we delve deep into the mechanism of space warping to handle unbounded scenes. Based on our analysis, we further propose a novel space-warping method called perspective warping, which allows us to handle arbitrary trajectories in the grid-based NeRF framework. Extensive experiments demonstrate that F2-NeRF is able to use the same perspective warping to render high-quality images on two standard datasets and a new free trajectory dataset collected by us.


Pipeline of F2-NeRF. (a) Given a large region of interest, we subdivide the space according to the input view frustums. (b) For each sub-region, we construct a perspective warping function based on the visible cameras. The densities and colors are decoded from the scene feature vectors fetched from the same hash table (d) but using different hash functions (c). See the paper for more details.


More results

F2-NeRF can be trained using trajectories with different patterns.


This study is supported by the Ministry of Education, Singapore, under its MOE AcRF Tier 2 (MOE-T2EP20221-0012), NTU NAP, and under the RIE2020 Industry Alignment Fund – Industry Collaboration Projects (IAF-ICP) Funding Initiative, as well as cash and in-kind contribution from the industry partner(s). Lingjie Liu and Christian Theobalt have been supported by the ERC Consolidator Grant 4DReply (770784). Peng Wang is supported by Hong Kong PhD Fellowship Scheme.


  title={F2-NeRF: Fast Neural Radiance Field Training with Free Camera Trajectories},
  author={Wang, Peng and Liu, Yuan and Chen, Zhaoxi and Liu, Lingjie and Liu, Ziwei and Komura, Taku and Theobalt, Christian and Wang, Wenping},