Modeling, simulation and visualization of forest cover is a very important aim for the sylviculture. Now the development of different techniques in tree and forest modeling, in GIS is sufficient to develop specific software used in forest simulation. Now, having a better way to represent and to interact with large models like forests are topics of high interest. After a short presentation of the project SILVES, we resent in this paper the design and implementation of a visualization program that involves two main features. It is based on the central data model, in order to display in real time the modifications caused by the modeler. Furthermore, it benefits from the different immersive environments which give the user a much more accurate insight of the model than a regular computer screen. Then, we focus on the difficulties that come in the way of performance.