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About this paper

Junze Liu, Kun Qian, Florian Dubost, Kai Zhong, Arvind Srinivasan, Nan Chen, Anping Wang, Sam Zhang and 3 more

Researchers at Unity Technologies investigate a paradox where Vision-Language Models (VLMs) can generate executable 3D scene reconstruction code but struggle with direct natural language spatial questions about the same image. The work establishes 3D geometric primitives as a "spatial language" for VLMs and proposes Code-CoT and S M -FT methods to enhance spatial reasoning, showing up to +17% improvement on real-photo benchmarks.

Key insights

  • VLM spatial knowledge is not uniformly accessible but is significantly entangled with the model's familiarity and prior training on specific scene-code languages, leading to up to 5.7 times performance variance.
  • 3D geometric primitives, when expressed in executable code, function as a compositional spatial vocabulary for VLMs, providing a structured scaffold for reasoning that can be leveraged at inference or training time.
  • Self-supervised distillation of primitive spatial knowledge through S M -FT can generalize effectively to out-of-distribution real-world images, suggesting a transferrable spatial understanding without requiring human labels.

Summary by alphaXiv.

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