Time-of-flight (ToF) devices have greatly propelled the advancement of various multi-modal perception applications. However, achieving accurate rendering of time-resolved information remains a challenge, particularly in scenes involving complex geometries, diverse materials and participating media. Existing ToF rendering works have demonstrated notable results, yet they struggle with scenes involving scattering media and camera-warped settings. Other steady-state volumetric rendering methods exhibit significant bias or variance when directly applied to ToF rendering tasks. To address these challenges, we integrate transient diffusion theory into path construction and propose novel sampling methods for free-path distance and scattering direction, via resampled importance sampling and offline tabulation. An elliptical sampling method is further adapted to provide controllable vertex connection satisfying any required photon traversal time. In contrast to the existing temporal uniform sampling strategy, our method is the first to consider the contribution of transient radiance to importance-sample the full path, and thus enables improved temporal path construction under multiple scattering settings. The proposed method can be integrated into both path tracing and photon-based frameworks, delivering significant improvements in quality and efficiency with at least a 5x MSE reduction versus SOTA methods in equal rendering time.

翻译：飞行时间（ToF）设备极大地推动了各种多模态感知应用的发展。然而，实现时间分辨信息的精确渲染仍然是一个挑战，尤其是在涉及复杂几何结构、多样材质和参与介质的场景中。现有的ToF渲染工作已展现出显著成果，但在处理涉及散射介质和相机扭曲设置的场景时仍存在困难。其他稳态体渲染方法在直接应用于ToF渲染任务时，则表现出明显的偏差或方差。为应对这些挑战，我们将瞬态扩散理论整合到路径构建中，并通过重采样重要性采样和离线建表，提出了针对自由程距离和散射方向的新型采样方法。进一步采用椭圆采样方法，以提供满足任意所需光子传输时间的可控顶点连接。与现有的时间均匀采样策略相比，我们的方法首次考虑了瞬态辐射度对完整路径进行重要性采样的贡献，从而能够在多重散射设置下实现改进的时间路径构建。所提方法可集成到路径追踪和基于光子的框架中，在同等渲染时间内，相较于最先进方法至少实现5倍的均方误差降低，在质量和效率上均带来显著提升。