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A Guide to 3D Point Cloud Segmentation for AI Engineers: Introduction, Techniques and Tools

What is 3D Point Cloud Segmentation?

A point cloud is a 3D data representation of the world collected by LiDAR sensors, stereo cameras, depth sensors or other scanning devices. It consists of an unstructured collection of individual points defined by x, y, and z coordinates.


Point Cloud Segmentation for Autonomous Driving Model (Source: https://github.com/PJLab-ADG/PCSeg)


Point Cloud Segmentation for Autonomous Driving Model (Source: https://github.com/PJLab-ADG/PCSeg)

Point cloud segmentation is the process of clustering these points into distinct semantic parts that represent surfaces, objects or structures in the environment. It involves classifying point labels to groups of points that belong to the same real-world element. For example, AI engineers may identity all points that comprise a car as the “car” object class. Other points would be segmented into classes like “road”, “building”, “tree”, “human” etc. based on what they represent in the 3D scene.

Why Segment Point Clouds?

Point cloud semantic segmentation is crucial for many applications as it enables object recognition, classification, and tracking in 3D environments. This allows robots and autonomous systems to understand their surroundings by identifying key objects like cars, roads, buildings, etc. Segmentation also facilitates semantic interpretation and understanding of complex 3D scenes by providing contextual information about the relationships between objects. This provides invaluable data for computer vision tasks.

Without segmentation, a point cloud is an incomprehensible jumble of input points. Segmentation brings order and meaning. It provides spatial information and structure crucial for real-world perception.

Techniques for Point Cloud Segmentation

Many techniques have emerged for tackling the complex task of point cloud segmentation. Here we explore some of the most common algorithmic approaches:

Region Growing Algorithms

Region growing methods take an iterative approach starting from a seed input point cloud. Neighboring points are progressively added if they meet certain geometric proximity or feature similarity criteria. The region expands until no more points satisfy the inclusion criteria.

Results of our semantic segmentation and labeling. Source: https://www.semanticscholar.org/paper/Semantic-Labeling-and-Instance-Segmentation-of-3D-Hu-Cai/1fa383f3cc13c7e4d679ad75ec7cc26e439303d0

Advantages of this technique include simplicity and intuitive principles. However, performance depends heavily on seed point selection and threshold tuning. Concave shapes and objects with heterogeneous features also pose challenges.

Clustering Algorithms

Clustering techniques like k-means, DBSCAN, and OPTICS treat segmentation as an unsupervised clustering problem. Points are grouped based on feature similarities like color, surface normals, etc. These methods can readily scale to large scale datasets.

A downside is making assumptions about cluster shape, density, and separation that may not match real environments. Noise and varying point densities also impact clustering approaches.

Graph-Based Methods

Graph methods first convert the irregular 3D point cloud into a graph representation. Each point becomes a node, with edges connecting neighboring nodes based on proximity.

Illustrative samples of the majority of classes in Sydney Urban Objects dataset. Source: https://arxiv.org/pdf/1704.02901.pdf

This fully captures the complex spatial structure and relationships within the 3D data. Sophisticated graph algorithms like normalized cuts, random walks, and conditional random fields (CRFs) can then identify semantic clusters corresponding to objects.

While powerful, a major limitation is the computational complexity required to construct and run algorithms on full graph representations of large point clouds.

Deep Learning-based Approaches

In recent years, deep learning has achieved state-of-the-art results on many point cloud segmentation benchmarks. Different neural network architectures have been proposed for consuming and extracting features from unstructured 3D point clouds:

  • Convolutional Neural Networks (CNNs) operate on voxelized versions of point clouds, enabling the application of standard 3D convolutions. However, conversion to voxels causes quantization losses.

  • PointNet pioneered direct processing of point sets using multilayer perceptrons (MLPs) and max pooling. This preserves detail but lacks local context modeling.

  • PointNet++ improves PointNet by applying hierarchical feature learning principles from CNNs. This better captures neighborhood information.

  • Graph Convolutional Networks (GCNs) perform convolutions based on dynamic point graphs to incorporate context from neighbors.

  • PointCNN applies learned x-conv operators based on hierarchical point groupings to capture local structure.

In general, deep learning methods excel at learning high-level semantic features from point data for accurate segmentation but have high computational requirements.

Applications of Point Cloud Segmentation

Point cloud segmentation enables transformative capabilities across many industries. Here we highlight some of the key applications and their impact.

Automating Logistics Operations

In warehouses, shipping ports and intermodal facilities, autonomous mobile robots, automated guided vehicles (AGVs) and self-driving container trucks rely on point cloud data to efficiently operate and safely navigate.

Point Cloud Segmentation for Drivable Area Detection: Point Cloud-Image Fusion Annotation

Segmentation allows these systems to precisely maneuver through tight spaces between shelves, containers, and pallets - reducing collision risks. By optimally mapping routes, robots also minimize energy use during goods transport. And by identifying and classifying different cargo items, automated loading/unloading and inventory management becomes possible.

Overall, point cloud segmentation provides the environmental awareness necessary for flexible automation to thrive in logistics hubs. This drives major efficiency gains, cost savings, and complements human workers.

Advanced Medical Imaging Diagnostics

In dentistry, detailed digital dental 3D models constructed via LiDAR scanning segmentation enable dentists to identify pathologies, analyze anatomy, and precision plan treatments like dental implants.


Display of Point Cloud Segmentation Results of Digital Teeth (Source: https://arxiv.org/abs/2112.04863)


Research on Disease Diagnosis Algorithm Based on Point Cloud Segmentation Data (Source: https://arxiv.org/abs/2112.04863)

In broader medicine, point cloud segmentation of MRI and CT scans isolates anatomical structures. This assists detection, diagnosis and monitoring of tumors, abnormalities and other conditions. It also enables targeted treatments. For example, accurate lesion modeling allows precise radiotherapy targeting for cancer care.

Drone-based Infrastructure Management

For cell towers, pipelines, railways and other assets, drone-based LiDAR provides detailed 3D LiDAR point clouds. Segmentation then automatically classifies each asset for tracking and condition assessments.

Surveying and Asset Management
Surveying and Asset Management

Separating ground and vegetation is also useful for monitoring clearance compliance and wildfire prevention. Overall, point cloud analytics from segmentation enables large-scale, automated asset management for infrastructure owners.

Increasing Safety in Construction & Mining

In mines, quarries and construction zones, point cloud data gives heavy machine operators enhanced perception and situation awareness. This allows safer navigation and positioning of excavators, dump trucks, cranes and more while performing complex maneuvers or when workers are near.


Quarries, Mining, and Industrial Material Handling
Quarries, Mining, and Industrial Material Handling

Ports and Logistics Centers
Ports and Logistics Centers

Cargo Transportation
Cargo Transportation

At shipping ports and railyards, segmentation enables automation of loading/unloading tasks by precision control of cranes and robotic arms manipulating containers and cargo.

Autonomous Mobile Robots

Accurate mapping and segmentation from point clouds is critical for applications like last-mile delivery, facility monitoring, and contactless healthcare robots. It allows assessment of drivable / traversable areas for efficient navigation while avoiding collisions with people.

Robotic solutions for unmanned delivery, inspection, and safety (Source: https://smprobotics.com/application_autonomus_mobile_robots/)
Robotic solutions for unmanned delivery, inspection, and safety

Robots with point cloud capabilities can take on crucial warehousing, industrial inspection, sanitation, and healthcare delivery tasks. Segmentation makes these applications possible.

Challenges and Future Developments

While point cloud segmentation has made great strides, many open challenges remain to achieve reliable performance in complex real-world environments:

Scaling to Massive Datasets: A key challenge is scaling algorithms to massive point clouds containing billions of points from city-scale LiDAR scans or large factories. This demands high computational power and memory management innovations. Ongoing work on hierarchical and distributed methods that leverage cloud computing aims to improve scalability.

Handling Noise and Outliers: Noisy data and outliers are common in real-world point clouds due to factors like sensor errors, occlusion, or weather conditions. Identifying and eliminating such artifacts via statistical preprocessing and filtering improves downstream segmentation accuracy. This remains an active research area as raw point data often contains noise and outliers.

Robustness to Variations: Point density, sampling patterns, and distributions vary greatly between environments and scanner positions, even for the same objects. Developing segmentation methods robust to such natural variations in data organization and density is an open challenge. Techniques emphasizing geometric relations rather than raw point features may prove more generalizable.

Partial and Occluded Data: Partial views and occlusion often lead to incomplete structures in point clouds. Developing algorithms that can intelligently reason for missing data and scene context could significantly improve segmentation reliability for real incomplete scans.

Coupled Reconstruction and Segmentation: Jointly optimizing reconstruction and segmentation could produce complete, structurally sound inputs by filling holes and compensating for imperfections in raw sensor data. This coupled approach is an emerging trend with initial promising results.

Obtaining Segmented 3D Training Datasets: While research drives new innovations, high-quality ground truth 3D training data remains critical for developing accurate segmentation algorithms. But collecting finely annotated point clouds poses a major bottleneck. We present two solutions to efficiently obtain segmented point cloud datasets:

Build Your 3D Dataset with Free Point Cloud Segmentation Tool

Obtaining quality ground truth 3D training data is crucial but challenging. To address this, BasicAI offers an easy-to-use cloud-based point cloud annotation tool for teams to efficiently segment and label datasets.

With BasicAI Cloud's point cloud annotation toolset, users can conveniently segment and review 3D objects directly in the editor. A wide range of shapes is available to accurately annotate complex scenes. Collaboration capabilities empower distributed teams to jointly work on large annotation projects. Key features include:

Leading autonomous vehicle, robotics, and drone companies use BasicAI's tooling to annotate point clouds for perception algorithm training. The high-quality datasets produced significantly improve model robustness and performance in the real world.

Get Your Segmented Point Cloud Datasets with BasicAI's Expert Annotation Services

While high-quality data is indispensable for AI systems, we know that the annotation process poses a major bottleneck. Data preparation can consume up to 80% of development time.

BasicAI Data Collection and Annotation Services

To help accelerate your project, BasicAI offers end-to-end 3D data annotation services. Our global team of experts specializes in producing finely segmented point cloud datasets tailored to your application needs. In point cloud equipment data collection and annotation client cases, we've worked with globally renowned manufacturers of automated lawnmowers, robotic vacuums, and automatic de-icing machines.

BasicAI delivers high-precision segmented datasets to provide the essential ground truth 3D data for your models to understand complex environments.

Case Study: Training Navigation Models for Robotic Vacuums

Background

A leading robotic vacuum manufacturer was looking to expand their products into the North American market. However, residential architectures and floorplans in North America differ considerably from other regions. This required building new navigation and mapping algorithms tailored specifically for North American homes. Thus, the company needed to collect extensive training data across diverse home environments in North America.

Solving the Challenge

To meet the need for comprehensive and varied data, our team:

  • Sourced numerous house floorplans throughout North America covering the full range from cramped urban apartments to sprawling rural estates.

  • Strategically set up furnishings, clutter, and other obstacles during data collection to simulate real-world conditions in different home styles, including objects like furniture, stuffed animals, shoes, clothing, and more.

  • Performed fine-grained semantic segmentation and labeling of the 3D point cloud and image data using BasicAI's annotation tools and experts. Labels indicated walls, doors, windows, obstacles, floor surfaces, and more.


RGB Point Cloud
RGB Point Cloud


Navigation Models for Robotic Vacuums
Navigation Models for Robotic Vacuums

In total, we were able to deliver fully annotated sensor data covering over 100 unique North American home environments and styles.

Outcome

Using BasicAI's extensively labeled 3D training datasets, the client was able to develop highly robust navigation and mapping algorithms specialized for North American homes. Their newest robot vacuum has seen significant performance improvements and reductions in collision incidents since launch. This has also enabled access to the large North American market, leading to substantial business growth.

Final Thoughts

Point cloud segmentation is undeniably transformative, fueling advancements in various sectors. While challenges persist, with constant innovation, the path ahead is promising. At BasicAI, we’re committed to facilitating this journey, aiding AI engineers in harnessing the full potential of 3D data. Through our tools and services, we aim to be the bridge to the next era of intelligent systems.