We present GI-GS, a novel inverse rendering framework that leverages 3D Gaussian Splatting (3DGS) and deferred shading to achieve photo-realistic novel view synthesis and relighting. In inverse rendering, accurately modeling the shading processes of objects is essential for achieving high-fidelity results. Therefore, it is critical to incorporate global illumination to account for indirect lighting that reaches an object after multiple bounces across the scene. Previous 3DGS-based methods have attempted to model indirect lighting by characterizing indirect illumination as learnable lighting volumes or additional attributes of each Gaussian, while using baked occlusion to represent shadow effects. These methods, however, fail to accurately model the complex physical interactions between light and objects, making it impossible to construct realistic indirect illumination during relighting. To address this limitation, we propose to calculate indirect lighting using efficient path tracing with deferred shading. In our framework, we first render a G-buffer to capture the detailed geometry and material properties of the scene. Then, we perform physically-based rendering (PBR) only for direct lighting. With the G-buffer and previous rendering results, the indirect lighting can be calculated through a lightweight path tracing. Our method effectively models indirect lighting under any given lighting conditions, thereby achieving better novel view synthesis and relighting. Quantitative and qualitative results show that our GI-GS outperforms existing baselines in both rendering quality and efficiency.
我们提出了GI-GS，这是一种新颖的逆向渲染框架，结合了3D高斯散射（3DGS）和延迟着色，实现了照片级逼真的新视图合成和重光照。在逆向渲染中，准确建模物体的光照过程对于实现高保真结果至关重要。因此，整合全局光照以考虑经过场景多次反射后到达物体的间接光照尤为重要。之前基于3DGS的方法尝试通过将间接光照表示为可学习的光照体积或每个高斯的附加属性来建模间接光照，同时使用烘焙的遮挡来表示阴影效果。然而，这些方法未能准确建模光与物体之间复杂的物理交互，使得在重光照过程中无法构建逼真的间接光照。 为了解决这一局限性，我们提出使用高效的路径追踪与延迟着色来计算间接光照。在我们的框架中，首先渲染G-buffer以捕捉场景的详细几何和材质属性。接着，仅对直接光照执行基于物理的渲染（PBR）。然后，利用G-buffer和之前的渲染结果，通过轻量级路径追踪计算间接光照。我们的方法能够在任意给定的光照条件下有效建模间接光照，从而实现更好的新视图合成和重光照。定量和定性结果表明，GI-GS在渲染质量和效率上均优于现有的基线方法。