  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.
