The feeling of presence is essential for efficient interaction within Virtual Environments (VEs). When a user is fully immersed within a VE through a large immersive display system, his/her feeling of presence can be altered because of disturbing interactions with his/her physical environment, such as collision with hardware parts of the system or loss of tracking. This alteration can be avoided by taking into account the physical features of the user as well as those of the system hardware and embedding them in the VE. Moreover, the 3D abstract representation of these physical features can also be useful for collaboration between distant users because they can make a user aware of the physical limitations of the others he/she is collaborating with. In this paper we present how we use the

The aim of this paper is to evaluate two new operating design modes and their collaborative metaphors enabling two actors, a design engineer and an end-user, to work jointly in a collaborative virtual environment for workstation design. The two operating design modes that correspond to two different design paradigms include : direct design mode (the design engineer manipulates objects while the end-user specifies their activity constraints) and supervised design mode (the end-user manipulates objects while the design engineer specifies their process constraints). The corresponding collaborative metaphors enable the two actors to manipulate objects while one (the design engineer) can express process constraints and the other (the end-user) can express activity constraints. The usability evaluation of the modes and metaphors consisted in placing a workstation design element on a digital workstation mock-up where a trade-off was to be found between process constraints and activity constraints. The results show that if we consider the completion time as the most important criterion to achieve, the direct design mode must be favoured. Otherwise, if the activity constraints are predominant, the supervised design mode must be favoured. In any case, the addition of an ergonomist's point of view is supported and warranted in order to enhance the effectiveness of the system.