Point cloud

A point cloud is 3D data that describes the surface of a building, site or object as a large number of individual points. Each point has X, Y and Z coordinates, and usually color and reflection intensity as well. The data typically comes from laser scanners or photogrammetry software and is exchanged in formats such as E57 and LAS.

What point clouds are used for

A point cloud is a measured record of what is actually there. It is used when renovating an older building, surveying a historic structure, or checking work on site against the drawings. The architect or modeler brings the cloud into their software as a reference and traces walls, slabs and levels over the points. In BIM this workflow is known as scan-to-BIM.

How it differs from a mesh or model

A point cloud is not a surface; there is nothing between the points. When it is dense it can look solid on screen, but you cannot assign materials to it or cut a clean section for drawings. For that you either generate a mesh from the points or use the cloud as an underlay and build a clean model on top.

In practice the biggest issue is file size. One scanning session can produce very large files, so clouds are usually thinned out, cropped and limited to the area being worked on. In visualization, a point cloud gives a reliable reference for placing surrounding buildings and terrain correctly.