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Polskiπ Roman Horologium: Sundial Shadow Simulator (2D)
A working sundial, not a walk-through model: real solar-position equations (declination, hour angle, altitude and azimuth) drive a gnomon's shadow across a horologium disc β the kind of public sundial that once stood in the Roman Forum itself β while a day-long shadow-tip trace and the Romans' own 12 unequal "temporal hours" are read out live.
The 3D "Roman Forum" is a decorative walk-through reconstruction β colonnades, a temple and wandering citizens β with lighting and atmosphere sliders but no physics underneath. This 2D companion goes the other way: it builds the real astronomy that made a Roman forum's public sundial actually work. Given a latitude, a day of the year and a time of day, it computes the sun's declination, hour angle, altitude and azimuth with the standard spherical-astronomy equations, then projects a vertical gnomon's shadow onto a horologium disc at the correct length (shadow = height / tan(altitude)) and direction. A toggleable trace plots the shadow tip's path across the whole day β the characteristic curve every sundial designer has to account for β and a live readout converts the current moment into the Romans' own timekeeping: twelve unequal "temporal hours" spanning sunrise to sunset (so an hour is longer in summer than in winter), and four night watches (vigiliae) after dark.
Canvas2D sundial driven by real solar-position equations β declination from day-of-year, hour angle from time-of-day, altitude/azimuth from latitude β with shadow length from gnomon height and a live day-trace of the shadow tip. Includes a Roman temporal-hour and vigil readout, dividing sunrise-to-sunset and sunset-to-sunrise into 12 and 4 equal parts respectively, as Roman civil timekeeping did.
2D Β· HTML5 Canvas 2D Β· 60 FPS target Β· runs fully client-side, no install