Despite of decades of research, creating intuitive and easy to learn interfaces for 3D virtual environments (VE) is still not obvious, requiring VE specialists to define, implement and evaluate solutions in an iterative way, often using lowlevel programming code. Moreover, quite frequently the interaction with the virtual environment may also vary dependent on the context in which it is applied, such as the available hardware setup, user experience, or the pose of the user (e.g. sitting or standing). Lacking other tools, the context-awareness of an application is usually implemented in an ad-hoc manner, using low-level programming, as well. This may result in code that is difficult and expensive to maintain. One possible approach to facilitate the process of creating these highly interactive user interfaces is by adopting a model-based user interface design. This lifts the creation of a user interface to a higher level allowing the designer to reason more in terms of high-level concepts, rather than writing programming code. In this paper, we adopt a model-based user interface design (MBUID) process for the creation of VEs, and explain how a context system using an Event-Condition-Action paradigm is added. We illustrate our approach by means of a case study.