Diff-PCR: Diffusion-Based Correspondence Searching in Doubly Stochastic Matrix Space for Point Cloud Registration

2023-12-31

arXiv.org

AI Summary

In point cloud registration, existing methods suffer from fixed iterative optimization paths, implicit correspondence refinement, and single-projection updates prone to local optima. This work introduces, for the first time, denoising diffusion models into the space of doubly stochastic matrices to explicitly model and optimize the distribution of matching matrices. Instead of fixed iterations, it employs the diffusion reverse process—enabling initialization from arbitrary inputs (e.g., white noise)—and integrates Sinkhorn regularization with differentiable geometric feature encoding to enable gradient-guided global matching search. Evaluated on 3DMatch/3DLoMatch and 4DMatch/4DLoMatch benchmarks, our approach achieves significant improvements in both rigid and non-rigid registration accuracy, correspondence quality, and robustness over RAFT-style methods and conventional feature-distance-based approaches.

Technology Category

• Computer Vision: Diffusion Models for Vision
• Search and Optimization: Sampling/Simulation-based Search
• Machine Learning: Learning with Manifolds

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs
• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking

Abstract

Efficiently finding optimal correspondences between point clouds is crucial for solving both rigid and non-rigid point cloud registration problems. Existing methods often rely on geometric or semantic feature embedding to establish correspondences and estimate transformations or flow fields. Recently, state-of-the-art methods have employed RAFT-like iterative updates to refine the solution. However, these methods have certain limitations. Firstly, their iterative refinement design lacks transparency, and their iterative updates follow a fixed path during the refinement process, which can lead to suboptimal results. Secondly, these methods overlook the importance of refining or optimizing correspondences (or matching matrices) as a precursor to solving transformations or flow fields. They typically compute candidate correspondences based on distances in the point feature space. However, they only project the candidate matching matrix into some matrix space once with Sinkhorn or dual softmax operations to obtain final correspondences. This one-shot projected matching matrix may be far from the globally optimal one, and these approaches do not consider the distribution of the target matching matrix. In this paper, we propose a novel approach that exploits the Denoising Diffusion Model to predict a searching gradient for the optimal matching matrix within the Doubly Stochastic Matrix Space. During the reverse denoising process, our method iteratively searches for better solutions along this denoising gradient, which points towards the maximum likelihood direction of the target matching matrix. Our method offers flexibility by allowing the search to start from any initial matching matrix provided by the online backbone or white noise. Experimental evaluations on the 3DMatch/3DLoMatch and 4DMatch/4DLoMatch datasets demonstrate the effectiveness of our newly designed framework.

Problem

• Finding optimal correspondences between point clouds efficiently
• Overcoming limitations of iterative refinement in existing methods
• Predicting searching gradient for optimal matching matrix using diffusion model

Innovation

• Uses Denoising Diffusion Model for gradient prediction
• Searches in Doubly Stochastic Matrix Space
• Iteratively refines matching matrix along gradient