sin(exp(3.5+sin(x^2)+0.6*cos(1.2*y^2))+pi*t)/20

A smoothed interpolation of the surface f(x,y) = sin(exp(3.5+sin(x^2)+0.6cos(1.2y^2))+pi*t)/20 evaluated at uniform intervals along x and y where t from 0 to 28.

A higher quality version is available for the collector (3 GB).