We present a parsimonious representation of velocity models which allows for user-defined placement of nodes. Mild restrictions are imposed on the data structure so that a computationally efficient algorithm can be used to smoothly approximate nodal values on finely sampled regular grids. The building block of the algorithm operates on one-dimensional arrays, allows for user-defined control of smoothness and guarantees that bounds are preserved. The specific data structure allows to carry out this process recursively to obtain multi-dimension smooth and regularly gridded velocity models.