Geometric antithetic sampling for rendering spatiotemporally modulated light

In ACM SIGGRAPH Asia Conference Papers, 2026 (Accepted)

We propose an efficient sampling technique for modulated light transport, including temporally modulated continuous-wave time-of-flight (CW-ToF) and spatially modulated structured light systems. The key idea is to form antithetic pairs by geometrically deforming the primal path such that the modulation terms have opposite signs. We demonstrate the usefulness of our method for reducing variance in MC rendering and in various downstream applications.

Abstract

We propose a geometric antithetic sampling strategy for efficiently rendering spatiotemporally modulated light, encompassing continuous-wave time-of-flight (CW-ToF) and structured light systems. This is motivated by observing that modulated light transport can be decomposed into a slowly varying geometric term and a rapidly oscillating modulation term, where the latter dominates variance. Our key idea is to construct antithetic sample pairs by geometrically deforming a light path so that the modulation term changes sign while preserving similarity in the underlying transport. In both CW-ToF and structured light, antithetic samples lie on an antithetic manifold—the set of configurations with opposite modulation—and we search along it to find the path most similar to a given reference path, thereby maintaining strong negative correlation between paired samples. For CW-ToF, this corresponds to shifting paths in optical path-length space, while for structured light, it involves deforming emitter samples along the spatial modulation manifold in projector-coordinate space. By unifying both cases under this geometric deformation framework, our method cancels high-frequency modulation components through paired samples, leading to significant variance reduction and enabling more efficient simulation of coded illumination and sensing systems in computational imaging.

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Cite

@inproceedings{kim26antithetic,
    author    = {Kim, Juhyeon and Cui, Jack and Jarosz, Wojciech and Pediredla, Adithya},
    title     = {Geometric Antithetic Sampling for Rendering Spatiotemporally Modulated Light},
    booktitle = {ACM SIGGRAPH Asia Conference Papers},
    year      = {2026},
    month     = dec,
    doi       = {10.1145/3829340.3842310},
    pubstate  = {Accepted}
}

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