ABSTRACT
From the previous case study, it can be seen that integrated CAD environments can be characterised by a number of features:
Appropriate representation
Whenever a designer chooses to use a particular CAD environment, he consequently commits himself to a particular underlying computational representation. This will inevitably affect the suitability of this environment for particular design tasks. A system having points as primitive elements (as is common in most desktop CAD environments), therefore, will not behave in the same way as a system in which points are defined in terms of pairs of intersecting lines (a line-based CAD environment allows for the description of lines in equational form, and can therefore potentially be parameterised), for example. The latter in turn is not the same as a system in which points are defined in terms of triples of intersecting planes (a surface-based system). Gehry’s choice of a surface-based CAD environment was capable of supporting the kinds of 3-D distortions needed to develop the Guggenheim form. Once a commitment has been made to a particular choice of CAD system, an appropriate representation is one which can effectively support the expression of design tasks and sub-tasks in the mind of the designer.
Comprehensive design description
As design information is expressed and described at various stages of the design process, an integrated CAD environment is capable of supporting both the expansion of this design information, and the application of analytical tasks upon it, as required by the designer.
Analytically driven
Different design practices develop their own particular types of CAD models that vary over time and in response to changing demands. They therefore need to be able to mould analytical applications to their own requirements. Analytical CAD functions need to meet temporal, designer-specified demands, to a degree which makes software expendable.
Support cyclical design development
As discussed in chapter 2 of this book, design does not progress in a linear fashion, but instead tends to be cyclical in character. This cyclical nature is determined by various factors. Conflicts and inconsistencies can arise between any of the many possible analytical criteria, e.g. between the positioning of a structural frame and a required spatial organisation. An early stage design response to a given brief can lead to a redefinition of constraints upon a scheme, together with a redefinition of the parameters associated with these constraints. Although cyclical design development needs to be supported, pragmatic factors invariably come into play, particularly in relation to the costs of making changes to detailed CAD models.
