Two-dimensional design drawings present difficulties for users to interpret into a 3D mental picture for constructability review, especially for today's complex projects involving many specialties. While a team of experienced professionals might perform the coordination quite well using only 2D CAD, oversights or field errors are not unusual and changes and rework in the later stages of the project are costly. The motivation for using 3D modeling, however, is not evenly distributed. While mechanical contractors, for example, have a strong motivation to use 3D modeling due to the greater volume requirements for their discipline, other disciplines such as fire protection and electrical have less motivation to go beyond 2D CAD. The result is an overall unwillingness to go to the perceived expense, in both time and money, of producing designs in a 3D format. It is important to examine the potential benefits more closely if general industry practice is to move in this direction. Furthermore, it is difficult to detect interference among small objects, and clearances (tolerances) are even more difficult to thoroughly scrutinize. Simply relying on human perception skill in this way to avoid changes and rework is not the most time-efficient solution. An even more low-technology approach is to simply circulate a specific design discipline's 2D drawings for comment without the benefit of a composite drawing file. Due to the limitations in 2D technology, spatial conflicts among different specialties are addressed through reviews of the design drawings by senior engineers and detailers. In piping (or conduit) system design, typically drawings from different design disciplines are brought into a single CAD drawing using external referencing techniques and then organized into a composite model, where objects with related categories are grouped into the same layer. Traditional Approach: 2D-based CAD:Ī result of past technology limitations, conventional 2D-based design has a certain inherent inefficiency. Historically, practical time considerations aided by reasonably uncomplicated design requirements yielded a design process wherein the designer converted a 3D mental image into abstract 2D representations. Understanding the designs requires the reverse learned skill of transforming the 2D model to a mental 3D image. Add to this process the complication of coordinating numerous 2D-based designs, and the opportunities for errors in design communication become apparent. Three distinctive levels of visualization technology use for design coordination can be identified. These levels are determined under the assumption that a VR environment is not a proper replacement for CAD, at least not presently. That is, CAD is taken for granted as being better suited for drafting while VR is deemed more suited for viewing and comprehension of models. The three levels are (1) 2D-based CAD, (2) 3D-based CAD, (3) 3D-based CAD supplemented or augmented with VR.