# PCR-CG: Point Cloud Registration via Deep Explicit Color and Geometry

## TL;DR

This paper presents PCR-CG, a novel point cloud registration method that explicitly incorporates color information through a 2D-3D cross-modality learning algorithm, significantly improving registration accuracy.

## Contribution

The paper introduces a new module that effectively embeds color signals into geometry representations for point cloud registration, enhancing performance over existing methods.

## Key findings

- Achieved 6.5% higher registration recall on 3DLoMatch benchmark.
- Improved registration recall by 2.4% over GeoTransformer.
- Enhanced registration accuracy by 3.5% over CoFiNet.

## Abstract

In this paper, we introduce PCR-CG: a novel 3D point cloud registration module explicitly embedding the color signals into the geometry representation. Different from previous methods that only use geometry representation, our module is specifically designed to effectively correlate color into geometry for the point cloud registration task. Our key contribution is a 2D-3D cross-modality learning algorithm that embeds the deep features learned from color signals to the geometry representation. With our designed 2D-3D projection module, the pixel features in a square region centered at correspondences perceived from images are effectively correlated with point clouds. In this way, the overlapped regions can be inferred not only from point cloud but also from the texture appearances. Adding color is non-trivial. We compare against a variety of baselines designed for adding color to 3D, such as exhaustively adding per-pixel features or RGB values in an implicit manner. We leverage Predator [25] as the baseline method and incorporate our proposed module onto it. To validate the effectiveness of 2D features, we ablate different 2D pre-trained networks and show a positive correlation between the pre-trained weights and the task performance. Our experimental results indicate a significant improvement of 6.5% registration recall over the baseline method on the 3DLoMatch benchmark. We additionally evaluate our approach on SOTA methods and observe consistent improvements, such as an improvement of 2.4% registration recall over GeoTransformer as well as 3.5% over CoFiNet. Our study reveals a significant advantages of correlating explicit deep color features to the point cloud in the registration task.