What Are Point Clouds, And How Are They Used?June 16, 2021
A point cloud is a collection of data points in space. It is a data collection defined by a particular system of coordinates. A point cloud can define a real or created physical system in a 3D coordinates system. Point clouds are used for 3D mesh and other modelling applications in 3D modelling. Point clouds typically are produced by 3D scanners which measure numerous points on the external surfaces. Point clouds are used for the performance of 3D scanning processes for many applications, including the creation of threeD CAD models for manufactured parts, metrology and quality inspections, and for a variety of applications for visualisation, animation, rendering and mass adaptation.
Point clouds are mainly the simplest 3D model form. They are individual collections of 3D-specific points. Each spot contains several measurements, including X, Y and z-axes coordinates, as well as additional data, such as an RGB colour value and a luminance value, determining how luminous the spot is.
Point clouds often align with three-dimensional models or other point clouds, a process called point set recording. The point cloud of a manufactured part can be aligned with an existing model for industrial metrology or inspection using industrial computed tomography and compares it to check the differences. Also from the point cloud can be directly extracted geometrical dimensions and tolerances. Whilst point clouds can be directly rendered and inspected, point clouds are frequently converted by means of a process commonly called surface reconstruction into polygon mesh or triangle mesh model, NURBS surface modelling or CAD modelling.
The converting of a point cloud to a 3D surface is technically many.
Some approaches such as triangulating Delaunay, alpha forms and ball pivoting, construct a network of triangles across the existing cloud vertices, while other approaches convert the point cloud into volumetric distance and rebuild the implicit surface thus defined with an algorithm of the marching cubes. One of the most important applications of point clouds is the development of digital twins of LiDAR point cloud assets.
How are they created?
Point clouds are created by the object or structure being scanned. Scans are performed either using a laser scanner or a photogrammetry process.
Laser scanners work by transmitting light pulses to an object’s surface, and measuring how long each pulse takes to reflect and to hit the scanner. These measurements are used to determine the precise position of the points in the object and then create a cloud of points.
The process of creating measurements from images is photogrammetry. The object uses pictures from different places to triangulate points on the object and trace them in 3D space. In this process, you can use almost any camera and again the final result is a cloud of points.
So, how do you use point clouds?
A point cloud mainly aims at creating a 3D model. You can see the point cloud itself as a 3D model, but often the point data is first converted into a polygon mesh, as most 3D software programmes use polygons.
Conversion of 3D Surface
Point clouds may be rendered and inspected directly or converted in different shapes and patterns into models.
Models for CAD
CAD is the term used to describe the processes of using computers to create, analyse or optimise digital models and has been widely used since the 1960s as an area of construction and design. CAD applications, developed by companies like Autodesk, Dassault Systems, Siemens PLM Software and PTC today, offer advanced capabilities in rendering & animation that allow engineers to view their product designs more effectively. 4D BIM, also known as building sequence, is a kind of simulation for virtual building engineering which enables engineers to visualise the project through a combination of 3D and project schedules.
The polygon mesh is made up of simple polygons and elements like vertices, edges, faces, polygons, and is used for the digital reconstruction of object surfaces (not volumes).
A triangular mesh is a kind of polygon mesh consisting of triangles joined by corners or curves. The vertices, edges and triangles are the part of triangular networks.
NURBS Surface Models
NURBS is a non-uniform rational base spline that is a mathematical model used to generate and display curves and surfaces. The NURBS’ mathematical complexity is often facilitated by easy-to-use 3D modelling and animated tools, such as Autodesk.
The precise 3D models made up of dot clouds can be used in different industries in many different ways. 3D models created by laser scans in the architecture industries help produce as-built drawings and models capturing current buildings’ condition and design. The accuracy of the 3D models allows for distance, area and volume measurement that is beneficial for construction and rehabilitation projects.
In manufacturing, point clouds and 3D models are popular as well. Parts and components can be scanned and converted into 3D models that can then be used for the refining and handling of an object in CAD programmes.
The Point Cloud Library is an open-source project and people choose to use point clouds. The cloud library is an open source framework with algorithms and tools to manipulate and refine your cloud data.
Poing clouds are relatively universal forms of 3D capture and storage and contain a range of usage cases in various industries.