Visual stimuli and reality
In virtual reality or in reality which is displayed on a monitor purposeful movements are quite difficult. Why is this the case? For example, in moving a cursor to an icon, there is a certain visual distance on the monitor which has to be transformed into a corresponding movement amplitude. The visual distance is not only determined by the distance between cursor and icon, but a correct perception requires that the distance of the observer from the monitor is taken into account. Size constancy is a classic topic in Perception. Even though on the retinae of the observer the distance between the images of cursor and icon changes when the distance of the observer from the monitor varies, perceived distance remains unchanged. Corresponding considerations hold for depth, even though depth constancy has received considerably less attention than size constancy.
In the simulation of endoscopic surgery, for example, virtual-reality procedures become more common. They allow more realistic simulation scenarios than other means. However, in VR systems the distance from the observer cannot always be set precisely. In addition, the camera can have a perspective that differs from that of the observer. In this case the meaning of visual stimuli can get lost, in particular their meaning with respect to distances in space. Possibilities to re-calibrate the visual space are often limited. We will explore possibilities and limitations of flexible calibrations of visual angles and visual disparities, both for the simple case of vision through an endoscope and the more complex case of manual work in a virtual space.