FreePart: Towards Generation-Friendly Decomposition for 3D Part Synthesis

Part-level 3D generation aims to synthesize complex 3D objects by decomposing them into semantically meaningful parts and generating them separately before assembly. However, we find that even semantically plausible decompositions can lead to substantially different generation difficulties and 3D reconstruction quality. When such decomposition choices are unfavorable, they can introduce errors that propagate through downstream generation, compromising the structural coherence and completeness of the resulting objects. To address this, we propose FreePart, a plug-and-play framework that searches for generation-friendly part decompositions and seamlessly integrates them into diverse part-level 3D generation pipelines. Specifically, we first introduce a Part-level Decomposition Assessment (PDA) to evaluate the generation difficulty induced by different decompositions. Guided by PDA, we then design a Multi-agent Collaborative Search (MCS) method, where three complementary agents iteratively diagnose, refine, and evaluate candidate decompositions, with valid decomposition states organized as a directed acyclic graph for efficient search. Extensive experiments across multiple generation pipelines demonstrate that FreePart consistently improves both part-level and overall-object 3D generation quality. Code and website are available in the supplementary material.