We propose a novel ray reordering technique to accelerate the ray tracing process by encoding and sorting rays prior to traversal. Instead of spatial coordinates, our method encodes rays according to the cuts of the hierarchical acceleration structure, which is called the hierarchy cut code. This approach can better adapt to the acceleration structure and obtain a more reliable encoding result. We also propose a compression scheme to decrease the sorting overhead by a shorter sorting key. In addition, based on the phenomenon of boundary drift, we theoretically explain the reason why existing reordering methods cannot achieve better performance by using longer sorting keys. The experiment demonstrates that our method can accelerate secondary ray tracing by up to 1.81 times, outperforming the existing methods. Such result proves the effectiveness of hierarchy cut code, and indicate that the reordering technique can achieve greater performance improvement, which worth further research.

翻译：我们提出一种新颖的光线重排序技术，通过先编码再排序的方式加速光线追踪过程。该方法摒弃空间坐标，转而依据层次加速结构的切割对光线进行编码，该编码称为层级切割编码。这种方案能更好地适应加速结构，从而获得更可靠的编码结果。同时，我们提出一种压缩方案，通过缩短排序键来降低排序开销。此外，基于边界漂移现象，我们从理论上解释了现有重排序方法无法通过使用更长的排序键获得更优性能的原因。实验表明，我们的方法可将二次光线追踪加速最高1.81倍，优于现有方法。该结果不仅验证了层级切割编码的有效性，更表明重排序技术能够实现更大的性能提升，值得进一步深入研究。