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Point Cloud as a Foreign Language for Multi-modal Large Language Model

arXiv cs.CV / 3/11/2026

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Key Points

  • The paper introduces SAGE, a novel end-to-end 3D multi-modal large language model (MLLM) that processes raw point clouds directly without relying on pre-trained 3D encoders.
  • SAGE uses a lightweight 3D tokenizer combining geometric sampling, neighborhood aggregation, and vector quantization to treat 3D data as a discrete token sequence, effectively extending the LLM's vocabulary.
  • The model employs a preference optimization training strategy with semantic alignment-based rewards tailored for complex 3D open-ended question answering, enhancing reasoning capabilities.
  • Extensive experiments show SAGE outperforms existing encoder-based approaches in 3D understanding benchmarks while offering better computational efficiency, generalization across different LLM backbones, and robustness to varying input resolutions.
  • This approach addresses key limitations of prior methods, such as semantic misalignment, resolution sensitivity, and computational overhead, enabling more effective and scalable 3D multi-modal language modeling.

Computer Science > Computer Vision and Pattern Recognition

arXiv:2603.09173 (cs)
[Submitted on 10 Mar 2026]

Title:Point Cloud as a Foreign Language for Multi-modal Large Language Model

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Abstract:Multi-modal large language models (MLLMs) have shown remarkable progress in integrating visual and linguistic understanding. Recent efforts have extended these capabilities to 3D understanding through encoder-based architectures that rely on pre-trained 3D encoders to extract geometric features. However, such approaches suffer from semantic misalignment between geometric and linguistic spaces, resolution sensitivity, and substantial computational overhead. In this work, we present SAGE, the first end-to-end 3D MLLM that directly processes raw point clouds without relying on a pre-trained 3D encoder. Our approach introduces a lightweight 3D tokenizer that combines geometric sampling and neighbourhood aggregation with vector quantization to convert point clouds into discrete tokens--treating 3D data as a foreign language that naturally extends the LLM's vocabulary. Furthermore, to enhance the model's reasoning capability on complex 3D tasks, we propose a preference optimization training strategy with a semantic alignment-based reward, specifically designed for open-ended 3D question answering where responses are descriptive. Extensive experiments across diverse 3D understanding benchmarks demonstrate that our end-to-end approach outperforms existing encoder-based methods while offering significant advantages in computational efficiency, generalization across LLM backbones, and robustness to input resolution variations. Code is available at: this http URL.
Comments:
Subjects: Computer Vision and Pattern Recognition (cs.CV)
Cite as: arXiv:2603.09173 [cs.CV]
  (or arXiv:2603.09173v1 [cs.CV] for this version)
  https://doi.org/10.48550/arXiv.2603.09173
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arXiv-issued DOI via DataCite

Submission history

From: Sneha Paul [view email]
[v1] Tue, 10 Mar 2026 04:22:40 UTC (4,255 KB)
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