The figure library

No figure on this site is a drawing that was made once and saved. Each one is a function: it takes a spectrum, an observer and a viewing condition, and returns SVG — so the same generator draws the chromaticity diagram under the 1931 2° observer and under the 1964 10° one without either being redrawn, and the difference between the two plates is a difference between two integrals rather than between two drawings.

That is the reason the collection can keep growing without the illustrations drifting apart. A generator is written once, checked once, and every essay that calls it inherits the same line weights, the same colour roles, the same behaviour in dark mode — and the same refusal to draw a colour the display cannot show as though it could. There are 155 of them so far, reached for by 469 essays in 697 distinct pairings — counting an essay once per generator it calls, however many figures it draws with it.

Reuse is the number that decides whether any of this is sustainable, which is why it is published rather than kept in a plan. A generator written for one essay and never called again is a design failure and not a neutral cost. The count beside each name is how many essays instantiate it, and the phase ledger refuses to advance if the ratio falls.

It is also the blast radius. Changing a generator changes every figure in its list at once, so that list is what has to be rebuilt and looked at before the change is believed — a bad shared helper once broke a hundred and eighty-one figures across four of these sites, and was caught only because somebody rebuilt immediately and knew where to look.

Each generator has its own page, drawn at its defaults — which is almost never how an essay calls it, since a placement states the numbers that essay is arguing about. What each essay asks for instead is on the observer index, which reads the observer and the unreachable fraction back out of the finished figures rather than out of the source that made them.

Each page also lists the options its generator actually reads, and that list is the one thing here worth checking a placement against. An option a placement passes that the function does not read is silently ignored: the figure draws its defaults under a caption describing something else, and every other gate passes on it. That is not hypothetical. Three figures on this site named the 1931 observer under captions about the 1964 one, for three phases, because a single generator spelled the option observer where a hundred and six spell it obs. Every placement in the collection is checked against these names now, and the lists are printed so a reader can check too.

Whatever colour is in any of these drawings began as a spectral power distribution and was integrated against a named observer before it was written down. The strip along each figure's bottom edge says which one — so a generator whose strip never changes is a label carrying no information, and the observer index is where that shows up.