Building assembly detailing using constraint-based modeling K. Nassar a, * , W. Thabet b , Y. Beliveau c a Department of Civil Engineering and Construction, Bradley University, 126 Jobst Hall, 1501 W. Bradley Avenue, Peoria, IL 61625, USA b 123 D Burruss Hall, Blacksburg, VA 24061-0156 540.818.4604, USA c 122 E Burruss Hall, Virginia Tech., Blacksburg, VA 24061-0156 540.818.4602, USA Accepted 4 September 2002 Abstract Constraint-based geometric modeling entails specifying geometric constraints to control the locations of the components in an assembly. Consequently, any future modifications of the components are governed by these constraints. In this paper, a set of constraint-based assembly operations for generating 3D details of building assemblies are presented. The operations constrain the locations and orientations of the components in a building assembly through a series of constructive steps and therefore allow for easier modification. These operations are used in a modeling system that extends the idea of constraint-based modeling to detailing architectural building assemblies. The system utilizes the constraint-based assembly operations, which employ traditional geometric constraints integrated with a set of constructive assembly operations. The constraint-based assembly operations allow for a more systematic generation of the assembly details, which can save repetitive work and reduce mistakes resulting from copying and pasting old details. Also, the technique allows the assemblies to be studied and analyzed. To illustrate this idea, a prototype 3D constraint-based system for assembling three-dimensional architectural details was developed. With the proposed system, the details of building assemblies do not need to be reinvented for every project. Examples of the proposed approach are provided and its limitations and benefits are discussed. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Constraint-based modeling; Assemblies; Building details 1. Introduction During the early and mid-1980s, CAD was gaining ground and becoming an efficient alternative to the drafting table. With the increased use of CAD, archi- tects were continuously devising ways to automate drafting and design tasks in order to increase their efficiency. Repetitive tasks were automated using predefined scripts, utilizing the various scripting lan- guages offered in the CAD systems (e.g. AutoCAD’s AutoLISP). Object-oriented data was added to lines, arcs and circles, and systems began recognizing them as doors, windows and doors. Object data was then extended to the third dimension, so architects could work in 2D and 3D. A number of software tools were devised in which architects can define their designs in 3D and the complete object model is maintained by the system. This started with simple ‘‘house model- ing’’ software marketed to help non-architects define their ‘‘dream house’’ (e.g. Home Architect, Home 0926-5805/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0926-5805(02)00090-0 * Corresponding author. E-mail addresses: knassar@bradley.edu (K. Nassar), thabet@vt.edu (W. Thabet). www.elsevier.com/locate/autcon Automation in Construction 12 (2003) 365 – 379