March 12, 2015 │ Scott Page │ http://www.aecbytes.com/
If you are unfamiliar with the terms; LiDAR, 3D laser scanning, point clouds, meshes, and NURBS, this article might scare you off, but I would hang on and hopefully learn something about reality capture from 3D laser scanners and the “point clouds” they generate. I will focus primarily on the use of point clouds into BIM platforms for architects and engineers.
Laser Scanning and BIM
GIS (Geographic Information System), ‘remote sensing’, stereo photogrammetry, and LiDAR are overlapping, competing technologies that very likely will find their place under the mother platform of BIM, working in concert to capture the world as it currently exists. Today’s architectural training is mostly directed towards creation, not the documentation of existing conditions. The “new” is simply more alluring to young, creative minds. It is far easier to create something new in BIM than it is to accurately model the terrain and detailed features of existing structures.
Documenting as-built conditions has historically been a tedious, often inaccurate process. 3D laser scanning offers a fast, accurate, albeit costly solution to this problem. The initial expense of the scanning is offset, however, by the speed, quality and quantity of the visual information produced. Scan data produces enormous file sizes. Accordingly, hardware must be up-to-date in order to accommodate the deluge of scan data. A minimum of 8GB of RAM (one cannot have too much RAM), 64 bit multi-core processors, and the latest generation graphic cards are required to handle point clouds efficiently. Fortunately, hardware costs have plummeted in recent years, while the software is racing to keep up with the processing advancements.
My first encounter with 3D scanning arrived in 2008 during a routine site visit to a house under construction for one of YouTube’s co-founders. A scanning service was employed to capture an area of complex geometry for a stone fabricator. Having used 3D modeling software since 1989, the value of laser scanning was immediate: Here was a way to capture as-built conditions into 3D, without having to laboriously transfer and interpret countless measurements and photographic references into CAD. It took several more years before I looked into 3D scanning, as applicable in architectural practice and BIM.
With the purchase 3D scanning equipment in 2011, I began testing scan data in a variety of software platforms including Revit 2013, ArchiCAD 15, Sketchup Pro , PointCab , and Pointools. Rapidform XOR, primarily a CAM application built around point cloud technology, is also a potential platform for architectural projects due to its robust tool set for meshes and NURBS. Transforming point clouds into polylines, solid models, and surfaces requires new training, of course, but it is both doable and rewarding once the work-flow is established.
Autodesk and Bentley have made the greatest inroads toward importing 3D scan data (point clouds) into their A/E product lines. Trimble’s recent acquisition of SketchUp, the fastest growing modeling software, and Tekla in 2011, provides a tantalizing window into the realm of possibility where specialized hardware and software are potentially crossed fertilized. Mergers and acquisitions don’t always result in product development, and may, in fact, stall promising technologies in favor of existing, profitable wares. So, it remains to be seen where point clouds will “make rain.”
Formats and Standards
3D imaging is a disruptive technology and has yet to find a settled position in the A/E world. With time, the process will be smoothly integrated into BIM platforms as file export standards such as the ASTM E57 format gain general acceptance. At present we must contend with a confusing mix of proprietary, ad hoc, and domain specific file formats. Just as DWG/DXF formats eased interoperability between many CAD programs, the fledgling open source E57 format will hopefully improve the importation and exchange of 3D scan data to most BIM platforms. The move to BIM is increasing the demand for 3D scan data from as-built conditions. In fact, the U.S. General Service Administration (GSA) has recently mandated the use of scanning: “Every federal facility must be documented in 3D.” “GSA's Office of the Chief Architect (OCA) is currently encouraging, documenting, and evaluating 3D laser scanning technologies on a project-by-project need basis. 3D laser scanning has become a prominent vehicle for acquiring building spatial data in three dimensions with high fidelity and low processing time.”
Scanning data and BIM are potentially well matched for as-built documentation—all that is needed is a common language and uniform tool sets to complete the marriage. 2D deliverables derived from point clouds will only improve the quality of traditional plan sets essential for planning departments and builders, even if the additional 3D information is not directly accessed or immediately appreciated.
Presently, we have an abundance of third party software solutions, plug-ins, and competing CAD platforms—a veritable Tower of Babel of technology. It’s nice to have the variety, but it’s a confusing, inefficient, and unsettled mess to work with. Equipment makers have added limited drafting and modeling tools to their registration software, but most choose to cooperate with the major A/E software providers for drafting and modeling solutions. Any program that has 2D capabilities, imports point clouds, and has the tools to limit and slice the point cloud can satisfy the needs of most users. Indeed, ArchiCAD and SketchUp, which currently offer no serious plug-ins for point cloud insertion, have little problem accepting scaled photographs (called “orthophotos”) that can be easily traced and dimensioned for 2D deliverables . This solution, while lacking the flexibility, elegance, and power of direct point cloud insertion into CAD/BIM platforms (such as AutoCAD, Revit, and Microstation), does the job fairly well.
Revit looks to be the most promising platform for point cloud importation, but is currently a disappointment from its over-decimation of the scan points , its tepid object recognition capabilities, and its lack of point cloud editing tools (to select and deselect subsets of points). With Autodesk’s recent acquisition of Alice Labs(in 2011), there is the hope for robust point cloud editing tools within Revit, and across the entire Autodesk product line. It remains to be seen which features Autodesk will adopt and maintain over time. Likewise, Bentley’s purchase of Pointools (also in 2011) adds great potential value to its line of A/E software products. Once BIM software developers perfect point cloud object extraction, data compression, and dimensioning, we’ll have an extremely powerful platform that melds the actual world with the fertile dreams of creative designers.
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