Ragged Neighborhood Attention for Spatiotemporal Neural Denoising of Deep Monte Carlo Renderings

In this work, we introduce the ragged neighborhood attention (RaNA) operator, which extends neighborhood attention to semi-structured deep images by dynamically resolving bin-to-bin relationships across spatial and temporal neighborhoods.

Deep images store a variable number of “bins” within each pixel, enabling deep compositing workflows with clean separation of overlapping objects, but Monte Carlo noise limits their practical use. Existing deep image denoisers are limited in quality, generality, and temporal processing because ragged bin neighborhoods are incompatible with fixed convolution kernels. We introduce the ragged neighborhood attention (RaNA) operator, which extends neighborhood attention to semi-structured deep images by dynamically resolving bin-to-bin relationships across spatial and temporal neighborhoods. Using RaNA, we build the first spatiotemporal neural denoiser for deep Monte Carlo renderings, termed RaNAD, with a multi-U-Net back-bone, multi-scale reconstruction, and an optimized CUDA implementation. RaNAD handles both deep-Z and deep-OID variants and supports temporal windows of up to 7 frames. Compared with the previous state of the art for deep image denoising, RaNAD improves denoising quality substantially while preserving the layered structure needed for deep compositing; when its output is flattened for evaluation, it also attains quality competitive with strong flat image denoisers. As a kernel-based method, RaNAD efficiently de- noises multi-AOV images, and temporal processing further improves quality and stability, making the method practical for offline production rendering and compositing workflows.