ocean_spectrum

Builds one ocean cascade's time-independent complex wave amplitude h0(k) from a JONSWAP directional spectrum: a Phillips energy core, Donelan–Banner directional spreading around the wind, a JONSWAP peak enhancement, and a k_min/k_max band limit that keeps each cascade to its own disjoint range of wave numbers. The result is randomised into a complex Gaussian so the same sea state produces a real random surface rather than a deterministic ripple. Runs when the sea state changes, not per frame — ocean_evolve animates the field it writes.