Virtual testing is a significant part of the product development process. It is possible to completely solve many problems through the interaction of geometric models, simulation tools, human models with the help of the appropriate software. If, in the course of testing, it is necessary to take into account subjective human perception, one may profitably use a full-size system for immersive projection (VR system). Such a system particularly makes sense in evaluating manufacturing, operating, application or maintenance. The human being interacts with a product whose physical shape does not yet exist in a virtual environment. In this case, the movements of product components are generally indirectly controlled by using a flystick, a wand or a similar input device. In reality many operations in maintenance are determined by the position and posture of the maintenance personal as well as by the mass, center of gravity and dimensions of the object to be manipulated. In a Mixed Reality Environment, it is possible to achieve a meaningful subjective ergonomic evaluation of the abovementioned operations. The paper elucidates a strategy to integrate real product components into a virtual environment. The user applies the real components or tools in the immersive full-size projection of the VR system. The VR system tracks the real object. This way, it is possible to move an invisible object model in the VR system in sync with the movements of the real object. The collision detection tool provided in the VR system is available and signalises contact of the real object with the virtual environment. The demonstrated solution is under consideration for the planning and ergonomic evaluation of service activities. The need of industry for a process that can be controlled in a safe manner is of particular concern. The solution given here is aimed at maintenance to be performed on the brake system of a light-duty truck.