We present a novel spatio-temporal reuse framework for time-resolved light transport, enabling efficient Monte Carlo rendering of time-of-flight (ToF) phenomena such as time-gated imaging and transient light capture. Existing ToF rendering methods are computationally expensive, scale poorly to complex dynamic scenes, and are therefore unsuitable for applications with strict latency constraints. To address this limitation, we draw inspiration from ReSTIR, a reuse-based technique for steady-state real-time rendering, and adapt its core principles to interactive-rate ToF simulation. However, naively applying existing ReSTIR methods to ToF rendering leads to severe inefficiency, as reused paths frequently violate optical path-length constraints and thus contribute little or no signal. We overcome this challenge by introducing a path reuse formulation that explicitly enforces physically valid optical path lengths. The key idea is path-length-aware shift mapping, a geometric transformation based on Newton's method that adjusts reused light paths to satisfy temporal gating constraints, inspired by specular manifold exploration in steady-state caustics rendering. The resulting framework substantially improves the efficiency of ToF rendering across a wide range of scenarios, including complex scenes with glossy or specular materials and dynamic motion. Our method supports both time-gated and transient rendering at interactive frame rates, enabling simulation under practical latency constraints. We demonstrate the effectiveness of our approach through two downstream applications, including shape reconstruction and navigation.

翻译：我们提出了一种新颖的时空复用框架，用于时间分辨光传输，从而实现飞行时间（ToF）现象（如时间门控成像和瞬态光捕获）的高效蒙特卡洛渲染。现有的ToF渲染方法计算成本高昂，对复杂动态场景的扩展性差，因此不适用于具有严格延迟约束的应用。为解决这一限制，我们从ReSTIR（一种用于稳态实时渲染的复用技术）中汲取灵感，并将其核心原理适配到交互速率的ToF模拟中。然而，将现有ReSTIR方法直接应用于ToF渲染会导致严重低效，因为复用的光路经常违反光程长度约束，从而贡献极少甚至无信号。我们通过引入一种显式强制执行物理有效光程长度的光路复用公式克服了这一挑战。关键思想是基于路径长度的移位映射（一种基于牛顿法的几何变换），其灵感源自稳态焦散渲染中的镜面流形探索，能够调整复用的光路以满足时间门控约束。由此产生的框架显著提高了ToF渲染在多种场景（包括具有光泽或镜面材料的复杂场景及动态运动）中的效率。我们的方法支持在交互帧率下进行时间门控和瞬态渲染，从而能够在实际延迟约束下进行模拟。我们通过两个下游应用（包括形状重建和导航）证明了方法的有效性。