Semi-Automatic Techniques for Generating BIM Façade Models of Historic Buildings

This paper describes a new semi-automatic approach developed for modelling historic building façades with Building Information Modelling (BIM) software. Two new developments for BIM software are presented in this paper. The first is a new library of parametric objects which are designed for modelling classical architectural elements from survey data. These library objects are dynamic and have parameters that can alter the shape and size of objects for multiple uses and not just once-off static modelling. The parametric architectural objects have been designed from historic manuscripts and architectural pattern books. These parametric objects were built using an embedded programming language within the ArchiCAD BIM software called Geometric Description Language (GDL). The second development which is described in this paper is a complete parametric building façade. This parametric building façade can be used as a template for fast and efficient generation of BIM façade geometry. The design of this parametric façade incorporates concepts from procedural modelling which is an automated approach to generating 3D geometries based on rules and algorithms. Parametric architectural objects are automatically combined with rules to generate many different façade arrangements which are controlled by user parameters. When automatically generating a façade, the initial position and size of elements are estimated using classical architectural proportions. Object can then be graphically edited individually or in groups to match the computer generated geometry to survey data. The parametric façade template has also been implemented with the Geometric Description Language for ArchiCAD BIM software. This enables the tools developed to utilise the full benefits of BIM software which includes automated construction or conservation documents, semantic object oriented objects based on IFC semantic classes, automatic lists of objects and material and the ability to add and link additional information to the model. Keywords—Building Information Modelling; Laser Scanning; Photogrammetry; Historic Building Information Modelling; Parametric Modelling; Procedural Modelling; Architectural Modelling; Cultural Heritage