Thomas — dx/dt = sin(y) − b·x, dy/dt = sin(z) − b·y, dz/dt = sin(x) − b·z. RK4 cyclically symmetric 3D ODE, not Rössler single-fold, not Lorenz butterfly, not Ikeda delayed-optical map. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.