To know what a Grafik Eye does, one must have some sense of what the design of interior lighting can do for a room. Proper lighting design can increase livability, usability, attractiveness, and value. Unfortunately, this is a much neglected topic; I have yet to see any spec or mass-market home that implements any of the design principles.
Rather than use all-purpose light sources, one assigns each light source or group a specific purpose. There are three main purposes: ambient or general illumination, task lighting, and accent lighting. The first purpose seems to speak for itself, but when you separate task and accent lighting from it, you find that general illumination does not need to be bright as we usually have it. It only needs to provide an ambient level, especially for moving about safely. It may consist of different areas, for instance brighter light over walkways.
Task lighting concentrates an appropriate level of light on an area used for a task, such as reading or cooking. It does not always need to be at a different level than ambient. Accent lighting highlights an architectural or decorative element such as a wall, a flower arrangement, or a sculpture. Obviously, assigning light sources to purposes requires many light sources.
An interior designer combines these types of lighting to "layer" a room, making it appear larger or more interesting. For instance, when you enter a room there may be a strongly illuminated sculpture in the foreground, a lower ambient level, a wash on the far wall, and a couple of brighter work areas in the room. Compare that with the typical "four white walls, one bright light" environment that we usually live in.
But to be most functional, purpose-designed lighting must be adaptable to the several potential uses of a room. For instance, the lighting levels will be quite different for a dining room between the Formal Dining, Cleaning, and Night Light uses (called 'scenes'). Likewise a home theater may have Watch Film, Cleaning, Entry/Exit, and Discussion scenes.
Controlling many light sources or groups through different scenes is what the Grafik Eye is used for.