Light-cone shell queries for scalable time-gated rendering

1Dartmouth College

In Computer Graphics Forum (Proceedings of EGSR), 2026

Teaser
Equal-time comparison of various time-gated rendering methods on the Dining Room scene (270k triangles, collimated beam emitter). BDPT and our method are shown at 30 s; Ellipsoidal path connections (EPC) [PVG19] require explicit ellipsoid–scene intersections and at this complexity produce a single sample in 11.4 m (shown at 1 spp). Our method replaces geometric intersections with point-based range queries over the light-cone shell, achieving time-gating cost independent of scene geometry and significantly reduced variance over both baselines (relMSE shown in insets).
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Abstract

Monte Carlo time-gated rendering requires sampling light paths that not only connect a sensor to an emitter, but which also have a total travel time that falls within a narrow interval, a constraint that is difficult to importance sample. We show that this problem has an underlying geometric structure: in the joint space of position and accumulated travel time, the points yielding a time-valid connection to a given query point form a light-cone shell. Prior methods sample this shell indirectly. Steady-state algorithms sample the full space and reject points outside it, giving high variance under tight gates. Ellipsoidal path connections target a single cone surface by intersecting an ellipsoid with scene geometry, coupling cost to scene complexity. Our key observation is that shell membership is cheap to test, needing only accumulated travel time and a Euclidean distance. We therefore store the vertices of traced light subpaths in a 4D spatiotemporal hierarchy and recast time-gated connection as a range query, using pruning and importance sampling over the shell to select time-valid vertices without intersecting scene geometry. This decouples the cost of time gating from scene complexity. Within a bidirectional path tracing framework, our method significantly reduces variance over existing approaches on scenes with up to 2.4M triangles.

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Acknowledgements

We thank the anonymous reviewers for their helpful suggestions and the members of the Dartmouth Visual Computing Lab for valuable discussions. We are grateful to the creators of the 3D assets used in our scenes: the city scene by Alex Samusenko (BlenderKit), tunnel road by Low poly 3d Models (Sketchfab), and car meshes by Comrade1280 (Sketchfab) and MaX3Dd (Sketchfab). This work was supported by NSF award 2403122.

Cite

Jack Cui, Juhyeon Kim, Adithya Pediredla, Wojciech Jarosz. Light-cone shell queries for scalable time-gated rendering. Computer Graphics Forum (Proceedings of EGSR), 45(4), July 2026. 
@article{cui26light-cone,
    author    = {Cui, Jack and Kim, Juhyeon and Pediredla, Adithya and Jarosz, Wojciech},
    title     = {Light-Cone Shell Queries for Scalable Time-gated Rendering},
    journal   = {Computer Graphics Forum (Proceedings of EGSR)},
    day       = {1},
    month     = jul,
    volume    = {45},
    number    = {4},
    year      = {2026},
    doi       = {10/rngr},
    publisher = {The Eurographics Association and John Wiley \\& Sons Ltd.}
}
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