1. A method for generating a hierarchical, multi-resolutional, adaptable model of a physical entity to enable subsequent manipulation of data during rendering, using one or more hierarchically organized multi-resolutional data trees T, each data tree comprising a plurality of nodes N k , each node having a grid with a fixed number of points to which data is associated, the method comprising the steps of: creating a geometry using one or more data trees; creating an associated overlay using one or more data trees, and enabling subsequent manipulation of data within the data trees during rendering, wherein at least one of the geometry and overlay comprises a formula to be applied to data within one or more data trees; wherein the geometry comprises the formula F G ({tilde over (T)} 1 ,. .. , {tilde over (T)} m ; α 1 ,. .. , α r ) where, {tilde over (T)}={{tilde over (T)} j } j ⊂T, and {α j } j are real-valued parameters representing properties associated with the geometry, and/or that the overlay comprises the formula F O ({circumflex over (T)} 1 ,. .. , {circumflex over (T)} n ; β 1 ,. .. , β s ) where, {circumflex over (T)}={{circumflex over (T)} j } j ⊂T, and {β j } j are real-valued parameters representing properties associated with the overlay, where the variables k, m, r, j, n and s are integers, and wherein {tilde over (T)} and {circumflex over (T)} are data trees T associated with the geometry and overlay, respectively.