Leveraging CloudCompare to measure grain geometries from 3D point clouds: a plugin for the G3Point algorithm

To assess the grain-scale morphology and size distribution of sediments which are important factors controlling the erosion efficiency, sediment transport and the aquatic ecosystem quality, we developed the G3Point algorithm to extract grain information from 3D point clouds. Field measurements can be very tedious and G3Point is a semi-automatic and non-destructive method developed to tackle the determination of the grain-scale shape of sediments in geomorphology. Initially developed with Matlab, G3Point i) segments a given 3D point cloud with sufficient resolution into individual sub-clouds, ii) fits ellipsoids to the sub-clouds and iii) computes metrics not only on the size and shape of grains but also on their orientation and organization. Unfortunately, the ergonomics of the Matlab code are not optimal to process and visualize 3D points clouds. The interaction with the user is based on scripts, Matlab is limited in terms of point clouds visualization functions, and it is not possible to edit point clouds directly in the graphical interface.
CloudCompare is a powerful free software for 3D point clouds and triangular meshes processing. Thanks to its plugin mechanism, we have fully integrated G3Point into the main application. It is available easily through the graphical user interface making the processing very productive and practical. The first step of G3Point, based on a trial-and-error approach, is much simpler with the plugin. Furthermore, even with a satisfying set of parameters, the segmentation needs often to be refined and CloudCompare allows to edit directly the point cloud. As CloudCompare includes many advanced tools for registration, resampling, color/normal/scalar fields handling, statistics computation and display capabilities, it is now possible to prepare data, precisely visualize them, apply G3Point and post process them with a single tool.