The development and testing of ubiquitous environments (places enhanced with sensors, public displays and personal devices) usually presents high costs, both due to the need to acquire specific hardware (sensors, displays, etc.), and the need to use, or even to build, a space wherein the physical system will be implemented. Consider, for example, the impact of testing a new ambient intelligence system to provide information in a hospital or in an airport. It is hardly feasible trying to prototype the system in the target environment due to the costs (e.g. of redesign) and problems associated with such approach. The use of three-dimensional virtual environments then arises as a solution to this problem. Using them, it becomes possible to simulate the use of technology without needing to purchase hardware, and without interfering with the physical environments in which the final system will be installed. Three-dimensional application servers such as SecondLife (secondlife.com) or OpenSimulator (opensimulator.org) provide an easy way to develop virtual worlds. A platform for the prototyping of ubiquitous environments is being developed at the Department of Informatics of the University of Minho, which is based on OpenSimulator: the APEX (rApid Prototyping for user EXperience) framework. At the moment, each new world has to be modelled manually, using an OpenSimulator compatible viewer, which makes this part of the process time-consuming and inefficient. This project’s objective is to study three-dimensional virtual environment modelling approaches, and to develop a module that integrates one of these approaches in the APEX framework to streamline the virtual worlds generation process. The tool developed is presented in this dissertation. It has reduced significantly the environment generation development time in the APEX framework. Moreover, a case study was developed during the project where the tool was used to build the environment. Despite the tool has been developed to meet the needs of the APEX platform, it can be quite useful for other OpenSimulator users.