Better NN-based decision surfaces

With viability envelopes, as with any NN-based decision surface, the higher the desired accuracy of the decision surface, the higher the sample density required. This research looked into getting the "most bang" for a given sample set size. The main approaches were:

• discard any samples which were perceived to be too far from decision surface (left)
• instead of sampling uniformly over the domain, vary the sampling density in proportion with the estimated distance to decision surface (right)