Hi-NeRF: A Multicore NeRF Accelerator With Hierarchical Empty Space Skipping for Edge 3-D Rendering

Neural radiance field (NeRF) has proved to be promising in augmented/virtual-reality applications. However, the deployment of NeRF on edge devices suffers from inadequate throughput due to redundant ray sampling and congested memory access. To address these challenges, this article proposes Hi-NeRF, a multirendering-core accelerator for efficient edge NeRF rendering. On the architecture level, a hierarchical empty space skipping (HESS) scheme is adopted, which efficiently locates the effective samples with fewer skipping steps and thus accelerates the ray marching process. Furthermore, to alleviate the memory access bottleneck, a vertex-interleaved mapping (VIM) method that eliminates memory bank conflicts is also proposed. On the hardware level, ineffective sample filters (ISFs) and voxel access filters (VCFs) are introduced to further exploit spatial sparsity and data locality at run-time. The experimental results show that our work achieves $2.67\times $ rendering throughput and $11.2\times $ energy efficiency compared to a SOTA NeRF rendering accelerator. The energy efficiency can be improved by $561\times $ compared to a commercial GPU.