Duplex-GS: Proxy-Guided Weighted Blending for Real-Time Order-Independent Gaussian Splatting

3D Gaussian Splatting (3DGS) achieves photorealistic rendering but requires global sorting for α-blending, causing noticeable “popping” artifacts and hindering deployment on edge devices. While sort-free Order-Independent Transparency (OIT) methods circumvent sorting, they introduce “transparency” artifacts and suffer from inefficiency due to the absence of physical constraints. To address these limitations, we present Duplex-GS, a dual-hierarchy framework leveraging proxy-guided spatial organization and a novel hybrid renderer that combines α-blending with reformulated Weighted-Sum Rendering (WSR). We introduce explicit ellipsoidal cell proxies to encapsulate local Gaussians, which enables efficient proxy-level rasterization. This strategy drastically reduces the overhead associated with global sorting. Furthermore, we propose a physically grounded WSR scheme with cell-level early termination, which restores the physical constraints absent in prior OIT-based 3DGS methods, effectively eliminating both popping and transparency artifacts. Extensive experiments on diverse real-world benchmarks demonstrate the effectiveness of the OIT-based paradigm for 3DGS, enabled by a practical dual-hierarchy implementation. Quantitatively, our method delivers high-fidelity real-time rendering, outperforming prior OIT-based 3DGS methods by 1.5×– 4× in speed, while reducing radix-sort cost by 29.8%– 86.9% compared with conventional α-blending without compromising visual quality. Project page: https://duplexgs.github.io/.