Modeling high-frequency outgoing radiance distributions remains a fundamental challenge in global illumination, especially for glossy and specular materials. Existing neural-based radiance caching methods commonly rely on positional feature encodings or spatially organized caches, which makes it difficult to represent sharp directional radiance variations without increasing the model complexity or sampling cost. To address this challenge, we propose OctaOctree, an efficient spatial-angular radiance representation for global illumination. OctaOctree organizes outgoing radiance with an adaptive octree in 3D space, and associates each spatial node with an octahedral directional map. By coupling the spatial hierarchy with direction-dependent storage, our representation allocates fine spatial resolution to local illumination and visibility changes, while using coarser spatial levels with richer angular resolution to capture glossy and specular radiance distributions. This design embeds a reflectance-aware spatial-angular prior directly into the radiance representation, reducing the burden on neural networks or reconstruction modules to recover high-frequency view-dependent effects from positional features alone. As a result, OctaOctree provides a compact and expressive neural encoding for a wide range of indirect illumination effects, from diffuse interreflection to sharp glossy reflections. Experiments demonstrate that our method produces high-quality, direction-aware global illumination with single network query at primary intersections, achieving improved fidelity and real-time performance compared with baseline neural radiosity and radiance caching approaches.

翻译：在全局光照中，对高频出射辐射分布进行建模仍是一个基础性挑战，尤其对于光泽和镜面材质而言。现有的基于神经网络的辐射缓存方法通常依赖位置特征编码或空间组织缓存，这使得在不增加模型复杂度或采样成本的情况下，难以表示尖锐的方向性辐射变化。为应对这一挑战，我们提出OctaOctree——一种用于全局光照的高效空间-角度辐射表示方法。OctaOctree在三维空间中使用自适应八叉树组织出射辐射，并将每个空间节点与一个八面体方向图相关联。通过将空间层级结构与方向依赖性存储相结合，我们的表示方法将精细空间分辨率分配给局部光照和可见性变化，同时利用更粗糙的空间层级（具有更丰富的角度分辨率）来捕捉光泽和镜面辐射分布。该设计直接将反射感知的空间-角度先验嵌入辐射表示中，减轻了神经网络或重建模块仅从位置特征恢复高频视点相关效应的负担。因此，OctaOctree为从漫反射互反射到尖锐镜面反射的广泛间接光照效应提供了紧凑且富有表现力的神经编码。实验表明，我们的方法能在主交点处通过单次网络查询生成高质量、方向感知的全局光照，与基线神经辐射度和辐射缓存方法相比，实现了更高的保真度和实时性能。