Abstract
Abstract. Since their introduction, modeling tools aimed to architectural design evolved in today’s "digital multi-purpose drawing boards" based on enhanced parametric elements able to originate whole buildings within virtual environments. Semantic splitting and elements topology are features that allow objects to be "intelligent" (i.e. self-aware of what kind of element they are and with whom they can interact), representing this way basics of Building Information Modeling (BIM), a coordinated, consistent and always up to date workflow improved in order to reach higher quality, reliability and cost reductions all over the design process. Even if BIM was originally intended for new architectures, its attitude to store semantic inter-related information can be successfully applied to existing buildings as well, especially if they deserve particular care such as Cultural Heritage sites. BIM engines can easily manage simple parametric geometries, collapsing them to standard primitives connected through hierarchical relationships: however, when components are generated by existing morphologies, for example acquiring point clouds by digital photogrammetry or laser scanning equipment, complex abstractions have to be introduced while remodeling elements by hand, since automatic feature extraction in available software is still not effective. In order to introduce a methodology destined to process point cloud data in a BIM environment with high accuracy, this paper describes some experiences on monumental sites documentation, generated through a plug-in written for Autodesk Revit and codenamed GreenSpider after its capability to layout points in space as if they were nodes of an ideal cobweb.
Highlights
1.1 Building Information Modeling (BIM) origins and Cultural Heritage sitesNotoriously, CAD systems were meant to offer the possibility of simultaneous design production as well as integrated specifications, blurring the distinction between designers and drafters
This relatively new approach implies that every object introduced is a geometric representation of real shapes or technical components, as in CAD systems, but it’s a data collector on its own, with specific meanings to the architect or the project manager. These elements provide an abstract computer representation of a physical world that is convenient for designers: a wall intended as an object, represents an actual wall in the physical world as well as a door as a digital object represents a real door, maybe connected to the previous wall. This advanced graphic duality is essential in design validation and it is considered the basic of Building Information Modeling (BIM), a coordinated, consistent and always up to date working process strongly supported by several software tools, continuously improved in order to reach higher quality, reliability, optimized scheduling, errors and costs reduction together with avoidance of any possible project misinterpretation (Garagnani, Cinti Luciani and Mingucci, 2011)
BIM has not to be considered only as a set of software to produce drafts and models but, on the contrary, as a pipelined process among designers, managers, engineers, architects and contractors, sharing a common language on a framework at their disposal (Eastman, Teicholz, Sacks and Liston, 2011). This way, BIM becomes a collaborative strategy in architectural design, in which the term “information” implies a sense of transparency among actors, in order to generate a team working culture devoted to efficiency and integration, focused on software mastering
Summary
CAD systems were meant to offer the possibility of simultaneous design production as well as integrated specifications, blurring the distinction between designers and drafters. Modern BIM environments, can create and manage parametric geometries, collapsing them in primitives that can be connected one by one through hierarchical relationships: this is a flawless procedure when creating simple objects from software libraries, where shapes and constraints are already set, but it’s much more difficult when components are generated to represent heterogeneous and original existing morphologies, for example acquiring data using digital photogrammetry or laser scanning equipment In this case BIM abstractions have to be mostly re-modeled by hand, since automatic feature recognition in available commercial AEC computer programs are still not effective, experimental and under development by several software houses. Similar considerations can be extended to digital photogrammetry, since photography has long been recognized as the most important form of documentation, especially in case of historic buildings; nowadays dense point clouds extraction from pictures is speeded up greatly by computer vision software, with evident benefits in 3d reconstructions
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