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ULIP: Learning a Unified Representation of Language, Images, and Point Clouds for 3D Understanding (2212.05171v4)

Published 10 Dec 2022 in cs.CV

Abstract: The recognition capabilities of current state-of-the-art 3D models are limited by datasets with a small number of annotated data and a pre-defined set of categories. In its 2D counterpart, recent advances have shown that similar problems can be significantly alleviated by employing knowledge from other modalities, such as language. Inspired by this, leveraging multimodal information for 3D modality could be promising to improve 3D understanding under the restricted data regime, but this line of research is not well studied. Therefore, we introduce ULIP to learn a unified representation of images, texts, and 3D point clouds by pre-training with object triplets from the three modalities. To overcome the shortage of training triplets, ULIP leverages a pre-trained vision-LLM that has already learned a common visual and textual space by training with massive image-text pairs. Then, ULIP learns a 3D representation space aligned with the common image-text space, using a small number of automatically synthesized triplets. ULIP is agnostic to 3D backbone networks and can easily be integrated into any 3D architecture. Experiments show that ULIP effectively improves the performance of multiple recent 3D backbones by simply pre-training them on ShapeNet55 using our framework, achieving state-of-the-art performance in both standard 3D classification and zero-shot 3D classification on ModelNet40 and ScanObjectNN. ULIP also improves the performance of PointMLP by around 3% in 3D classification on ScanObjectNN, and outperforms PointCLIP by 28.8% on top-1 accuracy for zero-shot 3D classification on ModelNet40. Our code and pre-trained models are released at https://github.com/salesforce/ULIP.

Learning a Unified Representation of Language, Images, and Point Clouds for 3D Understanding

The paper "ULIP: Learning a Unified Representation of Language, Images, and Point Clouds for 3D Understanding" addresses a critical challenge in 3D visual recognition: the limitations posed by datasets with insufficient annotated data and restricted category sets. Traditionally, the 2D domain has benefited significantly from integrating multimodal sources, such as language, to ameliorate similar limitations. The authors propose leveraging this approach to improve 3D understanding by introducing ULIP, a framework that learns a unified representation across images, texts, and 3D point clouds through pre-training. This endeavor seeks to enhance performance metrics in 3D classification tasks, particularly when data is scarce.

Core Contributions

Unified Triplet Learning:

ULIP employs a novel mechanism of unified representation learning through the formulation of object triplets consisting of image, text, and point cloud data. This design facilitates the alignment of 3D representations with vision-LLMs, specifically employing a CLIP-based model, which has established a common visual-textual space through extensive image-text pair training.

Adaptation Across Modalities:

The method demonstrates flexibility by being agnostic to 3D backbone network architectures. Thus, ULIP can seamlessly integrate with various existing architectures, enhancing their performance upon pre-training. This is evidenced when ULIP is applied to multiple backbones, including PointNet++, PointMLP, and PointBERT.

Performance Metrics:

ULIP achieves state-of-the-art results in standard and zero-shot 3D classification tasks. Notably, it raises the top-1 accuracy in zero-shot 3D classification on ModelNet40 by 28.8% compared to PointCLIP. Similarly, PointMLP sees approximately a 3% improvement in 3D classification on ScanObjectNN, marking significant advancements in accuracy metrics for both datasets.

Implications and Future Prospects

Theoretical Enhancements:

The integration of multimodal features into the 3D domain opens substantial avenues for research, especially in scenarios with limited data. It suggests a robust framework where cross-modal knowledge transfer can be pivotal for advancing 3D understanding.

Practical Applications:

These improvements have important implications for real-world applications such as augmented reality, autonomous driving, and robotics, where 3D visual recognition plays a crucial role. The ability to enhance model accuracy with limited 3D data collection lowers the practical barriers by relying on cross-modal pre-trained information.

Cross-Modal and Retrieval Potential:

ULIP enables not just improved recognition but also facilitates various cross-modal applications. An exciting application is the image-to-point cloud retrieval task, which underscores the potential for interactions between modalities, emphasizing the versatile applicability of ULIP.

Future Developments in AI

The paper signals a growing trend towards harnessing multifaceted data sources to enrich the learning capacity of AI models. Future research could explore expanding ULIP to other modalities or enhancing the scale and diversity of pre-trained datasets further. The extensive leveraging of existing knowledge across domains is likely to continue as the community seeks to push the boundaries of machine comprehension in complex environments.

Overall, ULIP stands as a testament to the promise of multimodal integration in overcoming existing limitations in 3D visual recognition. Its robust numerical results point towards a thoughtful advancement in AI, potentially setting a foundation for further cross-domain innovations and applications.

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Authors (9)
  1. Le Xue (23 papers)
  2. Mingfei Gao (26 papers)
  3. Chen Xing (31 papers)
  4. Roberto Martín-Martín (79 papers)
  5. Jiajun Wu (249 papers)
  6. Caiming Xiong (337 papers)
  7. Ran Xu (89 papers)
  8. Juan Carlos Niebles (95 papers)
  9. Silvio Savarese (200 papers)
Citations (138)
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