Lesson 3.5

Design Thinking/Module 3 · Ideate — generating spatial options

Lesson 3.5

Selecting and combining

Dot-voting and the desirability–feasibility–viability triangle

6 min Lesson 18 of 32

The hook
Your page is full — twenty sketches, three partis, a handful of borrowed principles. And now a problem that feels worse than the blank page: they're all kind of good. The lazy answer, 'pick your favourite,' undoes all the discipline of divergence, because your favourite is usually the first idea in disguise, or the prettiest sketch.

Convergence is a skill, not a shrug

Choosing badly wastes every hour you spent generating. Convergence has two enemies: premature attachment (falling in love so early you never considered the others) and the loudest-voice problem (the idea argued most forcefully, or proposed by the most senior person, wins). Both are cured by a structured, fair process that judges ideas against explicit criteria.

Dot-voting — narrow the field fast and fairly

Lay out all options, give each person a few 'dots,' have everyone vote simultaneously on the most promising. It neutralises the loudest-voice problem (the junior's dots count as much as the senior's) and surfaces collective promise fast. It's deliberately rough — it chooses the finalists, not the winner. Vote on promise, not polish; give few enough dots that people must prioritise.

The desirability–feasibility–viability triangle

Every idea must pass three tests. Desirability — do the people truly want it? (the human lens, judged against your brief and POVs). Feasibility — can it actually be built? (the technical lens, where the engineer's 'no' lives). Viability — does it make sense given budget, time, maintenance, lifespan? (the practical lens, judged against your constraints). The best idea sits in the centre overlap. Each missed circle names a failure: desirable+feasible but not viable = the beautiful budget-buster; desirable+viable but not feasible = the lovely impossibility; feasible+viable but not desirable = the soulless box.

Judging the finalists, worked

The sunken stepwell pit: desirable (poetic), but questionable feasibility (digging into a slab) and poor viability (expensive, inflexible) — a lovely impossibility, though it might survive as a raised platform. The triangle didn't just reject it; it pointed at the fix. The lighting-as-divider: desirable, feasible, and viable — dead centre, and notably not anyone's first idea. The folding-everything boat approach: desirable, feasible, mostly viable with cost to check.

Combine, don't just pick

The final design is rarely a single chosen idea — it's a combination of the best parts of several. The lighting-divider, the boat's double-duty furniture, and a raised platform aren't competitors; they combine into one richer design. This is why dot-voting cuts to a shortlist — so you have several strong ideas to recombine. You diverged to generate parts; you converge to assemble the best of them.

Every idea must pass three tests; the best idea sits in the centre overlap. Each missed circle names a kind of failure.

Go deeper — for practitioners & students

The three circles are checked by three different people at three different moments — desirability is the users' call (test with them in Module 5), feasibility the engineer's and builder's, viability the budget's and time's; a designer judging all three alone from the studio is often wrong about feasibility or cost. Weight the circles by project but never zero one out — an idea that completely fails any one circle is dead regardless of the others. And converging doesn't permanently kill the rejected ideas — if your chosen idea fails its prototype or test, you'll reconsider a runner-up, which is why you keep the full field; document the runners-up and why you set each aside.

Try it

1. Dot-vote your own field with a strict budget of four dots (judge the idea, not the sketch). Run each finalist through the triangle, naming which circle each misses and whether a tweak moves it to the centre. Find the centre idea and notice whether it was an early or a buried idea. Then combine — take the best parts of two or three shortlisted ideas into one integrated concept. Write a sentence describing it; this is what you take to Module 4.

Check yourself

3 quick questions — pick an answer to see why.

Q1Why is 'pick your favourite' a poor way to converge?

Q2What does each circle of the desirability–feasibility–viability triangle test?

Q3What move do beginners miss during convergence?

Key terms

Dot-voting: Laying out all options and having everyone simultaneously place a few dots on the most promising, neutralising the loudest-voice problem.
Desirability–feasibility–viability triangle: Three overlapping tests — do people want it, can it be built, does it make practical sense — with the best idea in the centre overlap.
Convergence by combination: Assembling the final design from the best parts of several shortlisted ideas rather than picking a single winner.

Recap

Convergence is a discipline, not a shrug, with two enemies — attachment and the loudest voice — cured by a fair process. Dot-voting narrows a full field to a shortlist fast and fairly. The desirability–feasibility–viability triangle judges the finalists against the three kinds of uncertainty, with the best idea in the centre and each missed circle naming a failure. And the move beginners miss: converge by combining, not just picking — the final design is a synthesis of the best parts of several ideas. The buried idea that wins is divergence's reward; the runners-up are your reserve if the loop sends you back.

Carry forward →

You have a chosen, combined concept that looks right on paper. But every idea looks right on paper. How do you make it testable — real enough to reveal its flaws, yet cheap enough that finding those flaws costs almost nothing?