Sundial
The same bank as The Riverbank, given a sky. The sun climbs, the shadows swing round and shorten, the water goes gold and then dark. None of it is kept between frames. Ask for six in the morning and you get six in the morning — the light at any hour is worked out from the hour, the way a sundial reads the time off a shadow rather than counting up to it.
One whole day
Drag the scene to walk along the bank; drag the hour to move the sun. Both are the same kind of move — changing an index.
A sundial, not a clock
A clock counts. It has to be wound, it has to be running, and if you want to know what six in the morning looked like you have to have been there at six.
A sundial doesn't count — it reads. The shadow is a function of where the sun is, and the sun is a function of the hour. That is this page: hand it any hour and it hands back that hour's light, with nothing in between.
So the hour slider is not a scrubber over recorded frames. There are no frames. Every position on it is computed the same way, and jumping from midnight to noon costs exactly as much as one tick.
How the light is worked out
The sun's height is a triangle wave through the day, smoothed by a
polynomial. No sin anywhere — which matters, because that keeps the
lighting on the same platform-stable path as the terrain, so the same seed at the same
hour looks the same on every machine.
A shadow is cast by looking a few squares up-sun and asking whether anything there is tall enough to block the light at this elevation. Low sun, long reach; noon, almost none. Nothing is traced and nothing is buffered.
The colour of the hour is a wash over the finished frame — warm and low at either end of the day, pale and flat at noon, deep blue at night with the glints on the water switched off.
Flat light, same bank: The Riverbank → · the whole valley: The Ruler Valley →
Ground from valleyGrid, props and lighting from
assets/bank.js, which this page shares with The Riverbank so the two cannot
drift apart. Day length only changes how fast the index advances on its own — the
picture at any given hour is the same either way.