The exercise was to think about how this solution is optimal only according to a small number of parameters, and that as we added more, the possible solution space was gradually reduced to a solution strikingly similar to what someone would design by hand.
The conclusion was that although tools can be very powerful, naive use of tools result only in naive solutions.
[0]: http://www.liftarchitects.com/journal/2012/5/28/printing-mat...
A lot of what I was doing wound up balancing stiffness to strength, so that when the parts/bridges were deformed, the stresses in the pieces remained reasonable. It's a reversal of the normal mode of thinking, where you have given loads, but the deformations are driving the load in a lot of cases (e.g. thermal, earthquake, wave).
The engineer in me looks at that structure, and I can piece out what all of the bits are doing -- there's a shear band, there's the truss supporting it, there's the opposing moment forces. Though, I look at the voids and think fatigue. I know that they're likely low load areas, which helps.
[edit] I'd also be interested in the material properties of 3d printing, if they've got any issues with tensile strength, brittleness, or anisotropy.
So you could say "oh, this structure supports these forces and it is assembled with 50cm and 25cm beams, optimize away".
Of course, an engineer can solve simple cases easily, but as you join compression and stretching forces in weird shapes it can get complicated fast.
Examples out of my head: stadium ceilings, small tools that are required to be strong in a specific way, bridges with limited foundation places, etc
I agree that 3d printing will help liberate designs from some of the constraints (namely, some of the fabrication constraints - they're some of the most difficult to incorporate in to an 'optimal' design) but I still think there will remain a number of considerations that design engineers must make that will involve sacrificing ideal structure for other advantages:
- Interfaces with other equipment / interoperability in a system: curved surfaces aren't too good at being bolted together. A spider-web mesh of structure forming a super-rigid but super-light chassis doesn't lend itself to fitting an engine inside. A design might need 30 years' service out of one part but maybe another part (eg: a hopper for corrosive mineral concentrate) only wants to withstand 3-5 years - it'd need to be easily separable from the parent structure so that can happen.
- Maintainability: holes in the parts where 3 beams of the truss converge are just asking for moisture ingress leading to corrosion. Some surfaces may not be easily painted because they're tucked away. Some areas need to be accessable to hand-sized objects in order to perform non-destructive testing for internal cracks/defects.
- Portability: it's all well and good to have a single, continuous structure until you have to transport it by truck to site hundreds of kilometres away and down a mine shaft to its intended location. A less optimal but heavier design may in fact offer a better whole-of-life cost if it can be fabricated in China and flat-pack shipped to where you need it, reducing the up-front cost compared to a more elegant, more optimised but more expensive to construct design that is then difficult to ship to site.
This is a topic that fascinates me. I really look forward to seeing what comes out in the next 10 years. Even in the last 5 years, I've gone from solving a 60000-element finite element model in 15 minutes, to solving an 80000-element model in 30 seconds. This is about the minimum size I need to do basic analysis on a complete structure, eg: a coal wagon. That smaller timeframe makes iteration so much more possible. I'll be able to now perform more than just iterative convergance on plate thicknessses - adapting the geometry of the model and remeshing is now within the realms of possibility. Similarly, pre- and post-processing software is becoming more capable of interpreting results and intelligently adapting the model to suit.
My biggest fear of this technology is that, like FEA makes possible already, many Engineers will fall to the trap of 'garbage in, garbage out'. It's very easy to construct a model that looks like it should represent reality and solves mathematically just fine, but doesn't give realistic or meaningful results. This technology looks like it could amplify that problem significantly. Presently, the only way you learn the unwritten rules of computational analysis is through tutorage by more experienced colleagues. A design that's far more complex because of more complex algorithms will be subsequently far more difficult for them to advise and correct on. Sometimes that simplicity of an inelegant and un-complex but well-understood structure is preferable.