Why Are We Here and Where We are Going: The Evolution of CAD

Abstract

This paper reviews architectural CAD in terms of its current use, development and status within the U.S. The characteristics of a new generation of architectural CAD system, called building modeling, are outlined. Criteria are developed for the evaluation of CAD systems that support building modeling. Some of the opportunities for universities growing out of building modeling are reviewed, including pedagogical implications and opportunities for research. 1. THE CURRENT CAPABILITIES OF COMPUTER-AIDED DESIGN AND DRAFTING By the mid-1970s, the first generation of CAD systems had evolved into powerful drafting editors, supporting the layout of a range of graphic primitives, their composition into symbols, cells and layers, and the management of graphic information using the electronic equivalent of pin-registered overlay drafting. The object to represent within CAD systems were drawings; that is, the units of composition were lines and text. Application languages were later added, allowing procedural definition of common compositions. Initially, procedural capabilities were directed toward complex drawing entities, such as dimensions and crosshatching. Later, they were used to deal with non-graphic information such as bills of material and with rule checking. Reports and schedules could be extracted from the non-graphic data associated with a drawing. Tests could be applied to the data. Architectural applications were developed that included wall editors that merged adjacent wall segments and allowed insertion of doors and windows. Because of the continued emphasis on the 9