3D landscapes generation is an interdisciplinary field that requires expertise in both computer graphics and geographic informations systems (GIS). It is a complex and time-consuming process. In this paper, we present a new approach to simplify 3D environment generation process, by creating a go-between data-model containing a list of available source data and steps to use them. To feed the data-model, we introduce a formal language that describes the process"s sequence. We propose an adapted format, designed to be human-readable and machine-readable, allowing for easy creation and modification of the scenery. We demonstrate the utility of our approach by implementing a prototype system to generate 3D landscapes with a use-case fit for multipurpose simulation. Our system takes a description as input and outputs a complete 3D environment, including terrain and feature elements such as buildings created by chosen geometrical process. Experiments show that our approach reduces the time and effort required to generate a 3D environment, making it accessible to a wider range of users without extensive knowledge of GIS. In conclusion, our custom language and implementation provide a simple and effective solution to the complexity of 3D terrain generation, making it a valuable tool for users in the area.