In this paper we present a new parametric approach based on environmental constraints, in order to generate digital models of architectural shape, directly within a three dimensional geo-referenced environment. Those constraints may be regarded as force fields with a specific spatial dimension. The system allows user, through implementation of specific generative procedures, to manage interactive architectural design processes. The designer is able to explore all possible infinite scenarios and the various possible design alternatives, by changing the parameters values and verifying in real time the results of the changes. Two experiments are presented.