Digital twins, virtual simulated replicas of physical scenes, are transforming system design across industries. However, their potential in radio frequency (RF) systems has been limited by the non-differentiable nature of conventional RF simulators. The visibility of propagation paths causes severe discontinuities, and differentiable rendering techniques from computer graphics cannot easily transfer due to point-source antennas and dominant specular reflections. In this paper, we present RFDT, a physically based differentiable RF simulation framework that enables gradient-based interaction between virtual and physical worlds. RFDT resolves discontinuities with a physically grounded edge-diffraction transition function, and mitigates non-convexity from Fourier-domain processing through a signal domain transform surrogate. Our implementation demonstrates RFDT's ability to accurately reconstruct digital twins from real RF measurements. Moreover, RFDT can augment diverse downstream applications, such as test-time adaptation of machine learning-based RF sensing and physically constrained optimization of communication systems.
@article{arxiv.2603.18026,
title = {Physically Accurate Differentiable Inverse Rendering for Radio Frequency Digital Twin},
author = {Xingyu Chen and Xinyu Zhang and Kai Zheng and Xinmin Fang and Tzu-Mao Li and Chris Xiaoxuan Lu and Zhengxiong Li},
journal= {arXiv preprint arXiv:2603.18026},
year = {2026}
}