The iterative nature of the algorithm permits users to terminate approximation algorithm based on operational criteria, such as median error, maximal error, or number of points used to construct the TIN. This is particularly relevant to real-time computer image generation as various scene rendering systems utilizing polygonal terrain patches have well defined limitations in order to maintain real-time performance. It also implies that the TIN generation procedure is automatically sensitive to smooth or rough terrain in that it selects only enough points to satisfy the required error constraints and tends to place points in those areas having the greatest topographic complexity.