  3D Gaussian Splatting has emerged as an alternative 3D representation for
novel view synthesis, benefiting from its high-quality rendering results and
real-time rendering speed. However, the 3D Gaussians learned by 3D-GS have
ambiguous structures without any geometry constraints. This inherent issue in
3D-GS leads to a rough boundary when segmenting individual objects. To remedy
these problems, we propose SAGD, a conceptually simple yet effective
boundary-enhanced segmentation pipeline for 3D-GS to improve segmentation
accuracy while preserving segmentation speed. Specifically, we introduce a
Gaussian Decomposition scheme, which ingeniously utilizes the special structure
of 3D Gaussian, finds out, and then decomposes the boundary Gaussians.
Moreover, to achieve fast interactive 3D segmentation, we introduce a novel
training-free pipeline by lifting a 2D foundation model to 3D-GS. Extensive
experiments demonstrate that our approach achieves high-quality 3D segmentation
without rough boundary issues, which can be easily applied to other scene
editing tasks.
