Paint pourings on fixed undulations

Top: side-on view, Middle: top view, Bottom: stretched-out view:
The above shows what has happened when paint was poured on a wavy surface. Gravity allows the paint to define the form as it flows from the top (point of contact) to either side of the surfaces until it hits the base below. The stretched-out view (bottom image) starts the process of compressing the depth to generate the human visual 2D experience.