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.
在逆向渲染中，准确建模可见性和入射光的间接辐射对于捕捉次级效应至关重要。由于缺乏强大的高斯光线追踪器，之前基于3D Gaussian Splatting（3DGS）的方法要么采用了简化的渲染方程，要么使用可学习参数来近似入射光，导致材料和光照估计不准确。为此，我们引入了用于逆向渲染的互反射高斯点云（Inter-Reflective Gaussian Splatting，IRGS）。为了捕捉互反射，我们采用了完整的渲染方程而不进行简化，并使用所提出的可微分二维高斯光线追踪实时计算入射辐射。此外，我们提出了一种高效的优化方案，以应对蒙特卡洛采样在渲染方程评估中的计算需求。此外，我们还引入了一种新颖的策略，用于在重新照明优化后的场景时查询入射光的间接辐射。在多个标准基准上的广泛实验验证了IRGS的有效性，展示了其准确建模复杂互反射效应的能力。