Turkish paper-marbling floats ink on a still bath and rakes it into swirls. Here the bath is a
Helix Noise field: each frame the pigment is carried along it by semi-Lagrangian advection.
Because the flow is divergence-free, the ink is only ever rearranged — bands stretch
and fold but never tear open or pile up. That is the defining property of an incompressible flow,
made directly visible. Swirl is the field's coherence; click or drag to drop
pigment, pick a colour below.