Concentric ripples z = sin(√(x² + y²))
Equation: z = sin(sqrt(x^2 + y^2))
With r = √(x² + y²), z = sin(r) depends only on distance from the origin, so level curves are concentric circles.
This is the t = 0 slice of a circular wave. The animated counterpart is the water-drop preset, where the phase travels in time.