In order to consider the effects of three-dimensional parameters, has been varied by multiplying it by a coefficient ranging 0.5-2.5. If this coefficient is higher than 2.5, only cells with are built and, in essence, the resulting cluster will be two-dimensional. If the coefficient is lower than 0.5, cells with are built.

To adequately examine this problem, the coefficient , from 0.5 to 2.5., has been varied during a set of one hundred experiments. The resulting clusters have been evaluated by using three indicators:

- number of built cells;
- standard deviation of the location of cells around its centroid;
- concentration of activities calculated by using the average number of the cells having the same activity of the central cell and located in the eight bordering cells.

Clearly, important differences exist in the resulting clusters. These differences depend on the variation of density that are obtained by using the third dimension. Thus, it can be stated that the third-dimension modifies crucial characteristics of the clusters.

**Further developments**

The model can be upgraded by introducing a further cost characteristic - urban code - in the equation 1. By introducing this element, it is possible to to establish an interaction between the user and the model, and to experiment with a possible evolution path of the cluster in relation to urban plans.