On Ray Reordering Techniques for Faster GPU Ray Tracing

TL;DR

This paper investigates ray reordering techniques to enhance GPU ray tracing performance, proposing a new method for secondary rays and demonstrating significant speedups on recent GPUs, despite some hardware overhead challenges.

Contribution

It introduces a novel ray reordering modification using termination point estimation, specifically optimized for secondary rays in GPU ray tracing.

Findings

Ray reordering improves trace speed by 1.3-2.0x on recent GPUs.

Reordering overhead remains a challenge in hardware-accelerated tracing.

The proposed method is agnostic to specific trace kernels.

Abstract

We study ray reordering as a tool for increasing the performance of existing GPU ray tracing implementations. We focus on ray reordering that is fully agnostic to the particular trace kernel. We summarize the existing methods for computing the ray sorting keys and discuss their properties. We propose a novel modification of a previously proposed method using the termination point estimation that is well-suited to tracing secondary rays. We evaluate the ray reordering techniques in the context of the wavefront path tracing using the RTX trace kernels. We show that ray reordering yields significantly higher trace speed on recent GPUs (1.3-2.0x), but to recover the reordering overhead in the hardware-accelerated trace phase is problematic.