1. A computer-implemented method for determining a volume of activation of neural tissue, comprising: receiving input data that includes values for stimulation parameters; defining an input vector using the input data; applying the input vector to a function that is generated from a computational training algorithm; obtaining, as output of the function and based on the applied input vector, a set of variable values for a parametric equation that includes a set of variables arranged in a relationship that defines a geometrical shape category that results regardless of values plugged into the set of variables, wherein each of the variables corresponds to a geometric feature of the geometrical shape category, such that different plugged in values for the respective variable results in different characteristics for the respective geometric feature; setting the variables of the parametric equation to the obtained variable values to produce a volume of activation corresponding to the stimulation parameters; and displaying the calculated volume of activation on a display screen.