I have spent the past month revising this project, and have come to the conclusion: I suck at parametric design. I set off with intentions of making the entire model parametric, but four weeks later I am left with a shambolic set of simi-parametric tools linked together with long manual processes and discarded ambition for the complex parts of the project.
Everything that I wanted to do with a parametric model could be achieved with a parametric model; this claim is the origin of the rhetoric for the flexibility of parametric models. In practice however, I did very little of the project with a parametric model, I did a bit of the project manually and I modified the the rest of the project so it was achievable. The result is a design that is distorted towards the strengths and away from the weaknesses of parametric tools. An example of this is the curves along the surface (illustrated below). The the curves are an explicit list of points that are wrapped onto the surface with a UV curve passed between them. Most of the time this curve looks straight, but at the ends of the surface (shown in the illustration in red) the UV curve starts to bend. The solution is to use a geodesic curve (the green one), but this breaks the relationships to the other curves. Given enough time, it would be possible to use straight geodesic curves but, given how long it would take, it is far easier to use UV curves and modify the design to allow the bend of the curve.
It is a trade off: will the 12 hours I spend fixing the parametric model be noticeable in the final design. And in some cases: is it faster to get the parametric model to conform to the real world, or is it faster to get the real world to conform to the parametric model. People mistakenly associate this decision with choice and blame the architect for being a luddite. But the decision is loaded and biases the design towards things that are easy to do parametrically and away from things that are hard to do parametrically. In this way, just like any other CAD tool, parametric designs can be read as being in the language of parametricisim – dare I quote Schumacher – biased towards the easy solutions.
So parametric flexibility is more than being able to do something, it is the ability to actually do it. For me, what I am able to do and what I actually do is quite different. I suspect the difficulty in doing some of these tasks is related using mathematics as the intermediate language between designer and parametric tool, but that is a topic for another post. Have you encountered a similar phenomena in your models?