Penetration-Free Compositional 3D Generation via Gaussian Surface Offset

Compositional text-to-3D generation aims to create multiobject scenes from text descriptions, yet existing approaches often suffer from severe inter-object penetrations during joint optimization, where entangled object representations lead to physically implausible scenes. To address this, we propose CompSAG to enable penetration-free and complete compositional 3D generation. Our key insight is a Gaussian surface offset (GSO) mechanism that mimics real-world repulsive forces to effectively resolve inter-object penetrations. The proposed GSO calculates offset values by aggregating repulsive forces from an object proxy surface, pushing apart the Gaussians in collision regions. Furthermore, during appearance optimization, we design a Gaussian surface rectification module to suppress the spiky geometric artifacts introduced by SDS. These are built upon a layout-guided scene initialization driven by a fine-tuned LLM, which provides precise spatial grounding from the text. Extensive experiments across diverse multi-object scenarios demonstrate that CompSAG produces complete, spatially coherent, and penetrationfree 3D scenes, outperforming prior compositional generation baselines.