COMPLEX ARCHITECTURE IN 3D: FROM SURVEY TO WEB F. Fassi a, * , S. Parri b a Politecnico di Milano, Building Environment Science & Technology Dep., Milan, Italy, francesco.fassi@polimi.it b Newthread s.r.l, Milan, Italy, parri@newthread.it KEY WORDS: Platforms for data collection, Interactive navigation, Web-GIS 3D ABSTRACT: The paper describes the final step of a four-year survey of Milan Cathedral. In the past years, several measurement surveys were conducted using innovative techniques such as laser scanning and close range photogrammetry. In particular, the last technique was the most studied, experimented with, and tested because it offers more suitable measurement of a huge complex marble structure. The final aim of the survey was to create a detailed 3D model of the big spire. The last phase of the job, here presented, was to transform the great static model into a 3D WEB BIM for managing and organizing the restoration work. 1. INTRODUCTION The survey work was developed over the last three years by the Polytechnic, BEST department, together with the Veneranda Fabbrica of Milan Cathedral to identify a modus operandi to protect, preserve, and add value to Milan Cathedral, while at the same time facilitating and boosting the capacity to monitor the cathedral’s heritage. Good geometrical knowledge is indispensable for that purpose; hence, the need for an accurate survey. To be in line with the times and exploit the undisputed potential offered by 3D for visualization and data interpretation, we chose to create a detailed 3D model of the whole complex structure. This model should allow visualization of both structural and ornamental parts, to decompose the spire in all of its building units, and to extract each type of measurements (at a maximum scale of 1:50). A 3D virtual model with these characteristics can then be used not only for size purposes but as a kind of abacus—a database for memorization and cataloguing useful technical/practical/organization data, usable for common on-site operations during ongoing, continual restoration and maintenance of Milan Cathedral. A 3D model will give us greater knowledge than the classic 2D mentality that still dominates representation and professional maintenance, restoration, and design jobs. 2. BIM: THE STATE OF ART The BIM (Building Information Modeling) concept came into being in 1987. It was called “virtual building” and was implemented for the first time by Graphisoft in Archicad. The National Building Information Model Standard Project Committee defines BIM as: “Building Information Modeling (BIM) is a digital representation of physical and functional characteristics of a facility. A BIM is a shared knowledge resource for information about a facility forming a reliable basis for decisions during its life-cycle; defined as existing from earliest conception to demolition.” A BIM is basically an integrated system used to design, represent, and maintain for the long term a built-up environment (Russell, 2008). BIM software combines digital three- or multi-dimensional representation of an object with a series of other data in a database (spatial position, technical characteristics, properties of materials and technological elements, implementation phases, and maintenance operations, etc.), thus defining a true geographical information system (GIS) of a building. Like a GIS, a BIM can also simply and immediately calculate quantities of a technical element, volumes, and surfaces and permits advanced queries that cross-check geometries, information, and relationships between elements. A BIM is the creation and management process of a building's "information model." The information can refer to the building's entire life cycle, from proposal to use and maintenance through implementation. Besides defining the process, the initials are also used to indicate the Building Information Model, that is, the virtual 3D model itself. That is why, commercially, the term also identifies new generation architectural CADs. These do not just design simple graphic elements (lines, polylines, circles, arches, etc.), but also allow designing the building's technical components (walls, supporting structures, windows, doors, etc.). Basically it is a modeling of objects in which, alongside the geometrical aspect, the user indicates and visualizes the element's functional and technological characteristics. According to the U.S. National Institute of Building Sciences (NIBS), several properties distinguish a BIM from the classical method. “A basic premise of BIM is collaboration by different stakeholders at different phases of the life cycle of a facility to insert, extract, update or modify information in the BIM to support and reflect the roles of that stakeholder” (Fallon, 2008). To do this, the system must favor “shared representation” both of information in the model and of the model itself. With this in mind, information must be understandable, usable, and modifiable for the different participants and be based on open, recognized standards. The BIM idea is about 20 years old, but it is only recently that there has been international awareness that BIMs can make design, construction, and different building operations more efficient, optimizing and speeding up building processes (Coates, 2010). Factors that have contributed to the growth and development of the idea of integrated systems to optimize production processes for architecture, engineering, and the building industry in general are surely the consolidated use of computers and the use of digital tools we cannot do without. This has involved professionals of all kinds, at all levels, 360° (Jung, 2011). This realization is joined by the birth of an increasingly important "three-dimensional mentality" favoring slow, but progressive, establishment of this type of approach.