Back to the drawing board

In a world of sophisticated 3D imaging and surface rendering, there is still a role for the sketch pad and the foam or clay model, Brian Davis discovers

Computer-aided design packages are an integral part of the designer’s armoury. Some designers claim products such as the Ford Ka, with its complex intersecting curves, would have been impossible to achieve without packages such as Catia and Alias to render surfaces and realistic images of three-dimensional objects. Others, though, stress the continuing importance of simple clay or foam models and the value of the human touch or sketch pad.

Professor John Drane, course director of industrial design engineering at the Royal College of Art (where Ford Ka designer Chris Svennson studied) says: `In many ways the use of computers is quite liberating for developing design, but we would not recommend using a computer to establish initial conceptual thinking.’

On the contrary, the RCA encourages students to develop drawing skills to create and communicate ideas. `I believe the computer can inhibit the freedom of thinking at the initial conceptual stage,’ says Drane. `But soon after this it would be pretty hard going, without the discipline of CAD, to create accurate models, like a car, working freehand.’

Dale Harrow, deputy course director in the RCA’s vehicle engineering design department, sees advantages and disadvantages to the CAD approach.

`Whereas traditional modelmaking involved sculpting a model, digitising it and then producing drawings, the real advantage of CAD is that it tends to knit all the various stages together better. This considerably reduces the design cycle time, and allows better integration between the design process and engineering.’

But Harrow admits it is difficult to visualise a complex 3D model on a 2D screen with any subtlety, to understand surface volumes and light effects. So he recommends producing clay or foam models from the CAD data, though the number of iterations is likely to be reduced.

Harrow was impressed by a recent demonstration of a full-scale 3D visualisation and projection system at the Tom Walkinshaw Racing design studios, in Leafield, Oxfordshire. A Silicon Graphics system projected full-size images of styling and engineering models which could be viewed directly on screen or via 3D spectacles to give a solid effect.

`The main problem was the prohibitive cost – about £3m – though considering it costs about £250,000 to produce a clay prototype, it may have potential.’

Belgian RCA industrial design graduate Bregt Ectors has created a luxury car using Alias Wavefront as a modelling system (with no sketch pad). At his degree show this month he plans to display a model of the Alias-designed vehicle using a Division VR package, projected by an SGI Onyx system in stereo onto a 67in Barco screen.

He also converted designs to Iges format for use as milling data by RLE in Germany, which produced a quarter-scale model in Urea plastic.

Some people think computers may lead – or mislead – the design. `It’s a real dilemma: sometimes the designer will be fooled into misinterpreting a surface that looks convincing on screen,’ says Harrow.

This is reflected in a new survey of 20 design consultants carried out by Tom Marshall-Andrews as part of his MPhil at the Glasgow School of Art. He discovered there was `almost an even split between those designers who thought computers enhanced creativity and those who thought it actually reduced it’.

Some designers insist CAD provides a more flexible approach to creativity with faster and easier feedback on making modifications to designs. Detractors argue that one can end up designing things which are easy to build as computer models, effectively letting the computer lead the design process rather than the designer.

Many designers say CAD reduces the use of a tactile approach to design – they prefer to make a foam model first, then digitise and manipulate it as a CAD model. So the introduction of cheaper and faster rapid prototyping is seen to promise great improvement to the design process.

Industrial designer Marc Tanner at international design consultant IDEO, which has a base in London, believes CAD offers big time savings. IDEO uses a variety of packages, from 2D software such as Freehand, Illustrator and Vellum for sketching ideas, to Pro-Designer and Alias Wavefront for 3D modelling of products from mobile telephones, Nike sunglasses to medical instruments.

`In the past, CAD was only used once people had selected a suitable sketch and made a physical model. But now I go straight from sketching ideas, often on screen, into Pro-Designer and Alias Wavefront, then swapping data with applications like Solidworks and I-Deas.’

Tanner still makes foam models: `There’s a point where you don’t know if you can tweak it any more unless you machine it in foam,’ he says. `We used to make the models first and then create CAD models. Now we develop the software models first and check out designs virtually.’

He says there is room for improvement. `Images still look flatter on screen and there is a need for good dynamic rendering for high-quality live-spun images. I’d also like to see things look better in 3D. It’s a bit like the difference between a 60ft IMAX screen and a conventional cinema.’

Even motorbike designer Bruce Renfrew, managing director of Leicester-based Renfrew Group, hasn’t thrown out his sketch pad yet. `Early sketches of concept design need to be on paper but then CAD systems affect design downstream of the initial idea,’ he says. The company has several seats of SGI’s Alias Wavefront, Parametric Technology’s Pro-Engineer and the Varimetrix solid surfacing hybrid. These are used to design a range of products including consumer, scientific and medical equipment, the Flymo lawnmower and the CCM 950 and CCM 604R motorcycles.

Renfrew says CAD offered advantages for design of the new CCM 604R motorbike. First, it accommodated the internal mechanisms and chassis accurately. Second, the body is made of a number of elements, some plastic and some steel, which all have to follow a common external surface. The CAD package ensured all of them did. Some intersecting surfaces would have been impossible to visualise without using a CAD package.

Renfrew says: `The way in which models are manipulated is still a bit creaky and I’d like the designer, as opposed to the engineer, to have a system which would allow a little more freedom. But CAD packages have become much easier to use.

`My only other issue is “realism” in terms of pictures and renderings which are used to excite the marketing departments. Alias is very good at that but some of the other CAD packages still need to catch up.’

At Ogle Designs, which works on products for the transport and medical equipment sectors, design manager Michael Phillips believes Alias is best for the slickest visuals when producing concept renderings. Ogle uses Pro-Engineer, Unigraphics, Autocad, 3D Studio Man and Corel Draw for 2D presentation work.

But Phillips insists: `You cannot substitute a 3D model for a physical hand-held model if ergonomics are important. Nothing beats picking up a lump of foam or wood and then resculpting it to get the feel just right.’

Ogle models the product in Alias, then engineers in Unigraphics and interfaces with networked CNC and stereolithograpy machines.

Gordon Sked, ex-design director of Rover and now a design consultant, argues: `Long before CAD systems were invented the designers, sculptors and engineers created curves that not only performed well but also looked right. The trouble now is that designers are perhaps placing a bit too much reliance on the CAD creation of the surface.’

Sked does not agree that you can achieve more complex surface shapes with CAD systems. But he adds: `I understand the concerns and worries that people have and recognise the importance of using packages like Alias to generate surfaces, and Catia to process them.

`Rapid prototyping and rapid CAD modelling is actually the best way to achieve the maximum level of confidence in the shortest possible time. You really do need to get something in your hand in order to prove that something is going to work.’