Wednesday, 9 March 2011

Making CAD become Computer Aided Design

CAD could become Computer Aided Design and support decision-making without too much trouble these days. However, it has to stop being Computer Aggravated Draughting dominated by the manufacturing viewpoint, which might present difficulties to some of the long-standing legacy CAD systems. Stakeholder viewpoints should be just that.
It is well-established that the way information is presented affects decision-making. Current CAD systems do not help most of the important decisions. Lets look at some examples, using a simple model of a ship's engine room with 2 x diesels, a control console, nominal box-shaped ballast water treatment, nominal emissions treatment on the exhausts. The model is extracted from a ship model, 'Imperva', by Lazy J, for which many thanks. Click on the pictures for embigment.

First, everything in a CAD model looks neat, perfect, finished. This could be fixed quite simply so that we know what is mature and what is still at sketch design.

Colour is traditionally used for system codes to reflect the organization of detailed design. This structuring principle may be irrelevant to a design review. The figure below uses colour and texture to indicate the maturity of the design to focus the decisions being made. The emission control is still pretty flakey, and is not ready for review. The engines have been decided, and are pretty much cast in stone. Both are in low-attensity colours. The items under review are the control system and the ballast water treatment.

Now to disrupt object-world thinking (Bucciarelli), converting the model to something like a cartogram. This is breaking 'attribute dependencies'.

Here, the size of the object does not represent how much space it takes up. It represents how much budget it takes up. The colour represents cost risk. The salience of the ballast water treatment box and the control system have increased, reflecting their importance to the customer's wallet. 'Distorting' size in this way seems heretical, but I think that is just habit. Proportional scaling should be entirely feasible. The design team might not like it; In my experience, spaces such as this are designed on a volumetric basis. Get the big bits in, add the middling size bits, then shove in all the little bits you can. The CAD model supports that viewpoint and does not ,say, challenge space / cost trade-off.

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