# Using Dynamo for Automatic Reconstruction of BIM Elements from Point Clouds
## 2 Materials and Methods  
This research was conducted in five phases (Figure 1). The first phase involved architectural surveying using 3D laser scanning and the registration of scans and creation of the point cloud. The second phase focused on developing computational algorithms for geometric reconstruction from the point cloud. The third and fourth phases consisted of a case study modeled using two different approaches: one automated using algorithms and the other manual, without any automation techniques. The fifth and final phase was dedicated to validating the results through data analysis and comparisons between both approaches using selected technical and methodological variables. This research was conducted over the years 2022 and 2023. The initial versions of the algorithms were developed in 2022 and were further refined in 2023, alongside the validation studies. In the modeling approaches we utilized, we classified them into three categories: manual, semi-automatic, and automatic. Manual modeling is performed without any algorithmic assistance. In the semi-automatic approach, the operator must provide more complex manual inputs to enable the algorithm to function, such as manually drawing the floor perimeter or adjusting the dimensions of elements created by the algorithm. The automatic approach involves minimal operator interference, limited only to common tasks across all approaches such as selecting points, choosing a base family for modeling, and defining the top and base levels of the element. It is conceivable to design algorithms that do not even require the user to select the family of levels. It is also common for a single project to have multiple levels, including intermediate levels within the same floor, making it essential to allow the operator to choose the top and base levels of an element, even if it is created automatically. For this reason, even though there are these minor inputs required from the operator, we still classify these approaches as automatic. Figure 1: Summary of the five phases of this research. The chosen case study was the Old Lifeguard Station of Fuseta, located in the south of Portugal in the Algarve region (Figure 2). Unlike traditional buildings, this has some peculiarities that make it challenging while bringing various elements for testing. The first feature noted was that it is elevated from the ground, leaving its entire lower structure of concrete beams and pillars exposed, and because it is located on Fuseta-Ria beach, it has much degradation in its structure that is in constant contact with the ocean water. The access to the building's main floor is via a ramp and stairs located on its perimeter, and the access to the roof floor is via an internal staircase. The slabs have different levels and slopes, and they have many deformities; the roof slab has a significant slope for the flow of accumulated rainwater. The building also contains a series of walls with different thicknesses and some curved walls. Due to its high degree of degradation and poor construction process, the base structure of the building, containing the beams and pillars, presents many deformations, deviations, and rotations in their axes, which requires more careful modeling to represent them in their correct dimensions and positions. The architectural survey was carried out through laser scanning using a Faro Focus3D S120 laser scanner (FARO Technologies, Lake Mary, FL, USA), a Trimble R8 GNSS GPS (Trimble Inc., Westminster, CO, USA) to record the control points, and photographic equipment and a DJI Phantom Four drone (DJI, Shenzhen, China) to make the photographic record of the building. All algorithms were developed and tested on a computer with an Intel(R) Core(TM) i7-7700K CPU @ 4.20 GHz, 48G B RAM, NVIDIA GeForce GTX 1060 6 GB graphic card, and Windows 10 as the operating system. The software chosen for BIM modeling was Autodesk Revit due to its high acceptance in the market [19] and because it contains the visual programming tool Dynamo.