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3D Shape Part Segmentation by Vision-Language Model Distillation


Core Concepts
A cross-modal distillation framework, PartDistill, that transfers 2D knowledge from vision-language models to facilitate 3D shape part segmentation, addressing challenges such as incomplete 2D predictions, inconsistent 2D predictions, and lack of geometric knowledge transfer across 3D shapes.
Abstract

The paper proposes PartDistill, a cross-modal distillation framework that transfers 2D knowledge from vision-language models (VLMs) to facilitate 3D shape part segmentation. PartDistill addresses three major challenges in this task:

  1. The lack of 3D segmentation in invisible or undetected regions in the 2D projections (issue I1).
  2. Inconsistent 2D predictions by VLMs (issue I2).
  3. The lack of knowledge accumulation across different 3D shapes (issue I3).

PartDistill consists of a teacher network that uses a VLM to make 2D predictions and a student network that learns from the 2D predictions while extracting geometrical features from multiple 3D shapes to carry out 3D part segmentation. A bi-directional distillation, including forward and backward distillations, is carried out within the framework, where the former forward distills the 2D predictions to the student network, and the latter improves the quality of the 2D predictions, which subsequently enhances the final 3D segmentation.

PartDistill can also leverage existing generative models to enrich knowledge sources for distillation. Extensive experiments demonstrate that PartDistill surpasses existing methods by substantial margins on widely used benchmark datasets, ShapeNetPart and PartNetE, with more than 15% and 12% higher mIoU scores, respectively. PartDistill consistently outperforms competing methods in zero-shot and few-shot scenarios on 3D data in point clouds or mesh shapes.

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Stats
PartDistill boosts the existing methods with more than 15% and 12% higher mIoU scores on the ShapeNetPart and PartNetE datasets, respectively. PartDistill achieves 12.6% higher overall mIoU than PartSLIP on the PartNetE dataset in the zero-shot setting. In the few-shot setting on PartNetE, PartDistill outperforms the fine-tuned Point-M2AE by 9.5% in overall mIoU.
Quotes
"PartDistill addresses three major challenges in this task: the lack of 3D segmentation in invisible or undetected regions in the 2D projections, inconsistent 2D predictions by VLMs, and the lack of knowledge accumulation across different 3D shapes." "PartDistill carries out a bi-directional distillation. It first forward distills the 2D knowledge to the student network. We observe that after the student integrates the 2D knowledge, we can jointly refer both teacher and student knowledge to perform backward distillation which re-scores the 2D knowledge based on its quality."

Deeper Inquiries

How can the proposed method be extended to handle multiple VLMs with different strengths and weaknesses in recognizing part semantics for various object categories

To extend the proposed method to handle multiple VLMs with different strengths and weaknesses in recognizing part semantics for various object categories, a few modifications can be made. Firstly, each VLM can be trained on specific object categories where it excels, ensuring that the strengths of each VLM are utilized effectively. The distillation process can then be adapted to combine the knowledge from multiple VLMs, taking into account their individual strengths and weaknesses. By aggregating the predictions from multiple VLMs, the model can benefit from a diverse range of semantic information, leading to more robust and accurate 3D part segmentation results across different object categories.

What other types of geometric features, beyond point-wise features, could be explored to further improve the 3D part segmentation performance

In addition to point-wise features, exploring other types of geometric features can further enhance the 3D part segmentation performance. Some potential geometric features to consider include: Surface Normals: Incorporating surface normal information can provide valuable insights into the orientation and curvature of surfaces, aiding in the segmentation of different parts based on their geometric properties. Curvature Information: Utilizing curvature information, such as mean or Gaussian curvature, can help distinguish between different parts based on their geometric shapes and structures. Local Descriptors: Extracting local descriptors, such as shape context or spin images, can capture detailed geometric information at different scales, improving the model's ability to differentiate between intricate part boundaries. Skeletonization: Representing shapes as skeletons or medial axis representations can offer a simplified yet informative view of the geometry, facilitating part segmentation based on structural characteristics. By incorporating a combination of these geometric features alongside point-wise features, the model can leverage a richer set of information for more accurate and detailed 3D part segmentation.

Can the proposed bi-directional distillation framework be applied to other cross-modal tasks beyond 3D shape part segmentation, such as 2D-to-3D object detection or 2D-to-3D scene understanding

The proposed bi-directional distillation framework can be applied to various other cross-modal tasks beyond 3D shape part segmentation, such as 2D-to-3D object detection or 2D-to-3D scene understanding. Here's how the framework can be adapted for these tasks: 2D-to-3D Object Detection: In the context of 2D-to-3D object detection, the framework can be modified to transfer knowledge from 2D object detection models to facilitate 3D object detection. The teacher network can be a 2D object detection model, and the student network can learn from the 2D predictions while extracting 3D object features for 3D detection. The bi-directional distillation process can enhance the quality of 2D knowledge and improve 3D object detection accuracy. 2D-to-3D Scene Understanding: For 2D-to-3D scene understanding, the framework can be adapted to transfer knowledge from 2D scene understanding models to aid in 3D scene understanding. By distilling information from 2D scene representations to 3D scene representations, the model can better comprehend the spatial layout and relationships within a scene in 3D space. The bi-directional distillation can refine the knowledge transfer process and enhance the overall scene understanding performance. By customizing the framework for these tasks, the bi-directional distillation approach can effectively leverage cross-modal information to improve performance in various 2D-to-3D conversion tasks.
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