In inverse rendering, accurately modeling visibility and indirect radiance for incident light is essential for capturing secondary effects. Due to the absence of a powerful Gaussian ray tracer, previous 3DGS-based methods have either adopted a simplified rendering equation or used learnable parameters to approximate incident light, resulting in inaccurate material and lighting estimations. To this end, we introduce inter-reflective Gaussian splatting (IRGS) for inverse rendering. To capture inter-reflection, we apply the full rendering equation without simplification and compute incident radiance on the fly using the proposed differentiable 2D Gaussian ray tracing. Additionally, we present an efficient optimization scheme to handle the computational demands of Monte Carlo sampling for rendering equation evaluation. Furthermore, we introduce a novel strategy for querying the indirect radiance of incident light when relighting the optimized scenes. Extensive experiments on multiple standard benchmarks validate the effectiveness of IRGS, demonstrating its capability to accurately model complex inter-reflection effects.

翻译：在逆向渲染中，精确建模入射光的可见性与间接辐射度对于捕捉二次效应至关重要。由于缺乏强大的高斯光线追踪器，以往基于3DGS的方法要么采用简化的渲染方程，要么使用可学习参数来近似入射光，导致材质与光照估计不准确。为此，我们提出了用于逆向渲染的互反射高斯溅射（IRGS）。为捕捉互反射现象，我们应用未经简化的完整渲染方程，并利用所提出的可微分二维高斯光线追踪实时计算入射辐射度。此外，我们提出了一种高效的优化方案，以应对渲染方程评估中蒙特卡洛采样的计算需求。进一步地，我们引入了一种新颖的策略，用于在重照明优化场景时查询入射光的间接辐射度。在多个标准基准测试上的大量实验验证了IRGS的有效性，证明了其精确建模复杂互反射效应的能力。