Colour lives in the fold.

THE SYSTEM BEHIND THE SURFACE

Inside Chiffon.

Each sheet is a band of cloth curled round an invisible axis — a partial cylinder — so a point on screen can lie on its near face and its far face at once: where a sheet wraps past its own edge you see both sides of the fold, one through the other. Every face at a pixel is found, sorted by depth and laid over the ground front to back. The cloth is thin, dyed and a little milky. Light crossing it travels thickness/|n·v|, so by Beer–Lambert a face turned away lets through exp(−σ/|n·v|): pale where the sheet faces you, deep where it turns, which is why sheer fabric gathers its colour in the folds and along its hems. Dyes mix by adding their absorbances, so overlaps deepen and shift hue the way layered chiffon does. The fibres scatter mostly forward, so only (1−g) of the scattering is lost for light coming through, while the studio light scattered back out of the cloth lifts a face-on sheet milky-white above its ground. Folds are broad panels joined by short steep turns, not sine ripples, so the colour gathers into fine lines on the turns. The flutter is a bending wave travelling down each sheet at an amplitude-based Strouhal number of 0.2 with a wave speed of 0.6 U — inside the range measured on real flags — so the wavelength is three times the amplitude and the wind sets only the tempo. Sheets off the focal depth blur by their circle of confusion, analytically.

Not a cloth simulation: the sheets hang on authored curves, the flutter is one travelling wave per sheet rather than a solved fluid–structure coupling, sheets can pass through each other where they cross, and they cast no shadows on the ground. The pleats are a profile across each sheet, not folds that can overlap themselves, and depth of field widens edges and averages out fine folds rather than blurring the whole image.

No published timing sample. Profile this effect on your target devices.