CAD Principles for Architectural Design

Peter Szalapaj

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781135389970
• Edition: 1
• Topic: Architektur
• Subtopic: Architektur Allgemein

CAD Principles for Architectural Design is aimed at design students and practitioners interested in understanding how CAD is used in architectural practice. This book makes connections between the basic operations that are common to most CAD systems, and their use in practice on actual architectural design projects.
The ways in which CAD is integrated into the design processes of several leading edge practices is illustrated. Arising from these case studies is the emergence of a contemporary phenomenon of integrated CAD, in which all aspects of design schemes are brought together within computational frameworks that support the analysis of design proposals. Szalapaj's view of CAD is one in which computers constitute a medium in which designers can express design ideas, rather than viewing computers as problem solving machines. For creative designers to successfully exploit CAD technology, CAD systems should reflect designers' intuitions as described by designers themselves

Part 1: Introduction

Chapter 1: Scope and Purpose

Most researchers in the field of CAD look upon the work that emerged from MIT as long ago as the early 1960s (Coons, 1963; Sutherland, 1963) as being the start of computer aided design (CAD) applications related to architectural design. The increasing frequency of releases of new CAD software since then, however, seems to be inversely proportional to the number of new technical developments in this field. Although there have been many new technological advances, these have largely come from other areas of computing, and the principles associated with the functionalities of CAD software systems have stayed fundamentally the same. What appears to be of greater significance, however, are the changes in the ways in which CAD is used in architectural practice. CAD in architectural education, therefore, should recognise and reflect these changes, and offer more to students than mere training or rote-learning of particular technical CAD system facts. By placing CAD in the context of contemporary architectural environments, and looking at case studies of the use of CAD in practice, I hope that students can glean not only technical, but also CAD principles of a more strategic nature.

This book is concerned with the use of CAD in design contexts, and its central premise is that it is the design intention that drives the ways in which architectural form is modelled within CAD environments. It is becoming increasingly both necessary and feasible for architectural designers to express their design intentions as directly as possible, in order to show their clients and fellow design specialists the salient features of a design scheme. With recent improvements in both computer hardware and software technology, CAD is no longer just a drafting tool used in the post-design phases of a project. On the contrary, it is a medium which is increasingly used throughout all phases of the design process.

Even though CAD software (e.g. for rendering) has improved dramatically in both speed and quality in recent years, many respected architectural practices still consider it to be of more importance to be able to communicate the essential architectonic design ideas, rather than to generate seemingly sophisticated renderings that often obscure rather than illuminate the design concept. This should be a warning to students in schools of architecture who, once they become seduced by the deceptive possibilities offered by rendered models, find it more difficult to pare down the presentation of their schemes to the key concepts within them.

A conscious effort has been made in the text to approach CAD from a design perspective rather than from a technological one. The focus in a technological perspective is on the medium or on the technology. A design perspective, on the other hand, focuses on the possibilities offered by the technology for supporting expression in design. The development of computer applications in design has often been seriously hindered by technological approaches (Bijl, 1993). Very often, so-called ‘CAD experts’ and CAD tutors in schools of architecture work outwards from the technology asking ‘what might the user be able to do with this new technology?’ rather than ‘what might the user want to do with this new technology?’. It is the latter that is the concern of this book.

A designer’s architectonic ideas, therefore, should be central to the organisation and generation of CAD models. The expression of ideas, rather than the representation of end form, has two primary objectives. Firstly, it enables the designer’s realisation and clarification of a design concept, and secondly, but most importantly, it enables the designer to critically assess these ideas in relation to the contextual situation and brief. From my own experience of teaching CAD to architecture students over recent years, the greatest fear that students have of CAD is the fear of obsolescence. They worry about whether they will be prepared for the marketplace unless they are intimately familiar with the latest version of a particular piece of software. I hope that by attempting to place CAD within the context of design, certain CAD principles can be derived from this process which ease these worries and encourage them to exploit their strengths as designers, irrespective of all the commercial hype.

The traditional view of CAD in architectural practice has been that CAD systems should be used to communicate already completed design schemes. Commercial CAD systems have focused predominantly on mechanising the end process of architectural production, i.e. on the graphical communication of design descriptions to fabricators, estimators, approval bodies, etc. They have facilitated limited analysis of established design proposals according to pre-set criteria such as lighting levels or energy loss. Evidence from the case studies presented later in the book, however, will show that there is now substantial impetus in architectural practice to interface CAD systems with analytical tools as much as possible in early design stages. In other words, CAD in practice is moving towards assisting design itself, rather than being a mere production tool.

If it is indeed the case that there is a trend towards the increasing use of CAD in earlier design stages, then we should expect that computational expressions in the form of CAD models should be structured in ways which support designers’ intuitive critical assessments of them. This structuring of models will then support the modification and development of the initial design ideas. The repeated transformation of ideas, CAD expressions, and intuitive analysis, can then develop in a cyclical manner until an end proposal is reached. Intuitive analysis which mediates between a design idea and its representation, can itself be computationally supported by a range of complementary methodologies that relate to well-understood analytical frameworks (e.g. energy calculations, lighting, structural analysis, design theoretic analyses, etc.).

Whereas scientists use technical and rationalistic problem solving methods embodied in an information processing model to solve problems, architects conversely propose initial solutions (without being fully convinced of their suitability) as a method of more completely understanding and pre-structuring the complexities of an architectural brief. Only by proposing an initial solution and then making a critical assessment of it, can architectural designers fully understand the complexities of the brief in a manner which could not be adequately achieved by rational analysis alone.

In a study of the design methods used by a selection of London housing architects, Darke recognised their intuitive selection of what she described as primary generators in the preparation of initial proposals or conjectures:

‘The term primary generator does not refer to that image [i.e. conjecture], but to the ideas that generated it’ (Darke, 1979)

In Darke’s study, she discovered that the initial solutions which produced better projects were designed by architects who had realised strong conceptual ideas in the initial proposal stages, and that these architects had maintained the generative and directive force of those initial ideas throughout the extent of proposing and refining a solution.

Darke’s study highlighted the dualistic relationship between concept and parti (schematic drawings, often abstract plan drawings, but sometimes sections), which is managed intuitively by the architectural designer. The ability to intuitively select conceptual ideas which in turn generate effective organisational proposals is one factor which distinguishes gifted designers from those less so. In architecture, like sculpture or the graphic arts, two states of externalisation exist, the model and the work itself. Unlike the finished work, the model does not attempt to become the ultimate state of externalisation, however, but exists simply to represent it. But the status of the model incorporates two roles, firstly to represent the ultimate physical state of the finished work, but also and very importantly, to represent or to express the internalised ideas of the designer.

Traditionally, the former role of the model as representation is well supported in CAD systems. Sophisticated modelling and rendering techniques have achieved levels of representation which are almost indiscernible from the physical world. In its capacity to represent volumetric qualities, the model (whether physical or virtual) provides the ultimate referent. Many students think that in producing a highly rendered realistic CAD model, they have satisfied the objectives of their design project. Sadly, it is all too often the case that although the model might appear impressive, the essence of the design proposal is nowhere to be seen. The realism instead becomes what Bijl has called a realistic deception (Bijl, 1995).

Models used to communicate design intentions and ideas externally to others are often very different from design drawings or design models. From the first hesitant pencil scribblings, through conceptual proposals to development drawings, design representations serve an alternative purpose, to externalise or to express the ideas of the designer, not for others but for the designer alone. Mark Hewitt (Hewitt, 1985) makes the distinction between objective and subjective drawings. Whereas the former present the building the latter are made for the edification of the designer himself. This is an important distinction because Hewitt’s subjective drawings are an integral element in the period of activity when a design is being formulated. It is then that the relationship between a designer’s idea and its expression is explored and developed. In direct contrast to the subjective drawing, the objective drawing is prepared after the period of design formulation has ceased, and therefore plays no part in the modification of ideas.

Recognising the importance of graphical expression during design, the characteristics of expressions can be categorised into three broad groups related to the stage of development of the proposals. Graves, in relation to drawn expressions, has named these stages referential sketches, preparatory studies and definitive drawings (Graves, 1977). The referential sketches are the very immediate direct recording of influential ideas. These may be related strictly to the contextual environment of the project, or like Le Corbusier’s carnets, may be combined with daily observations or travel notes. In relationship to the earlier discussion of conceptual generators, the sketchbooks become highly personalised records of the influences, often combined with highly schematic organisational partis. Referential sketches can also encompass textual descriptions and thoughts, scrapbook paste-ups, and of course generalised architectonic observations.

By the initiation of the so-called preparatory study, a tentative connection between conceptual generator and preliminary organisational parti begins. Confidence in the suitability of a proposal is impossible at this point, but it is important that initial proposals are expressed to enable their critical analysis and, therefore, the development of an enhanced understanding of a design project. At the stage of the preparatory study, some initial attempt is made to relate schematised diagrams of circulation, planning, structure, etc., to a suggested architectonic formal proposal. This indicates a designer’s inherent ability to intuitively relate architectural form with structured understandings of its implication, or more importantly, the potentiality of forms related to desired structured relationships. During this stage of design, a rapid succession of proposals is externalised and related continually to the programme requirements and the conceptual generators. The nature and influence of such conceptual generators may vary continuously during this stage of design formulation, but a strong relationship between conceptual ideas and organisational proposals is highly important in generating an identity and direction.

Once the so-called definitive drawing stage is reached, the dialogue of concept and organisational parti has reached a level at which the designer is satisfied of its efficacy. However, beyond the level of basic schematic organisation and volumetric architectonic approach, a level of resolution is still absent. Although a satisfaction of the solution is achieved, further development of organisation and relationships is required.

It is at this stage, therefore, that a resolution of the basic criteria of structure, zonal planning, servicing, construction and volumetric composition is carried out. Post-rationalisation analyses of design precedents (Baker, 1989) powerfully demonstrate the degree to which this resolution can be carried out by gifted designers. It is at this stage particularly that higher level ordering techniques are used to enable and enhance this procedure. Proportional systems, geometric grid organisations and techniques of symmetry are among the many methodologies used to govern organisational refinement.

During the preparatory study stage of design formulation, the immediate generator and referent are the referential sketches (i.e. conceptual ideas). During the development of definitive drawings, the preparatory studies, or chosen architectural parti, take prominence as the generator and controlling influence. Whilst conceptual ideas are still significant in providing the ultimate anchor to the design, the relationship between definitive drawing and preparatory studies is more immediate in the designer’s consciousness.

In all stages of design, it is the ability of the designer to express or to externalise his ideas to the limit of his understanding at that particular stage which is crucial. No attempt is made to exhaustively describe or resolve all aspects of the design. What is omitted in an expression is often as important as what is included. Dimensional accuracy is often absent – approximate dimensions are sufficient, with intuitive understandings of scale and proportional relationships being of greater importance. Partial models display similar characteristics. Often being very crude and having incomplete descriptions of elements, they are, however, effective tools to enable an appreciation of spatial relationships, for example. In all cases, a strong relationship exists between the components of an expression, and the designer’s idea which this expression signifies. For example, in separate expressions, an identical graphical element may be used, but may signify two entirely different ideas. Therefore, despite attempts to standardise graphical descriptions with convention systems, a semantic specificity exists between designer and expression.

The activity of analysis instigates change and hence the development of design. In Clark and Pause’s work (Clark and Pause, 1985), for example, the range of analytical criteria include the following: structure, natural light, massing, the relationship of plan to section, symmetry and balance, the relationship of circulation to use, the relationship between repetitive elements and unique elements, the relationship of individual units to the whole scheme, geometry, the extent to which elements have been formed out of additive and subtractive operations, the hierarchical structure, and the parti diagram.

We need to investigate the ways in which these and other criteria might be supported in terms of CAD principles. In the case of structural, energy, and lighting analysis, this would entail the use of already developed software in these areas, ensuring that the CAD data is both represented and presented in a form to which this analytical software can be applied. In looking at massing, the user needs to be competent in volumetric block modelling techniques. In describing relationships between plans and sections, and between circulation and use, this implies the ability to overlay information within the CAD environment. Repetitive elements can be represented effectively within CAD environments through the use of symbols. The description of relationships between units and wholes requires the understanding and use of more advanced CAD principles such as the expression of parametric relationships and object-oriented techniques. Geometry, symmetry and balance imply the understanding of basic CAD operations that either transform existing objects, or allow the construction of new objects in relation to existing ones in user-controlled ways. Addition and subtraction imply an understanding of how to use boolean operations. Hierarchical structuring implies knowing how to represent information at different levels of detail. Parti diagrams can be viewed in terms of user-defined grid systems.

Already we have begun to develop mappings between analytical criteria that are highly relevant to the process of designing, and CAD principles that require understanding in order to support design development. The above is by no means an exhaustive set of mappings. Clark and Pause represent just one source in this area of design. It is also beyond the scope of this book to arrive at some definitive list of mappings, as this will inevitably be subjective and variable amongst design practitioners. It is merely an attempt to adopt a certain approach and way into CAD that may be more palatable to design students than technology-driven approaches.

Analysis, therefore, should be seen as the binding link in a cyclical progression of idea–expression–analysis–idea ... end proposal. CAD needs to support critical dialogues between design ideas and their...