Study of sunlight and shadow effects on the city has become more accessible with the development of 3D city models. It allows measuring when and how an object is exposed to the sunlight, which enables conducting many related studies such as energy analyses or urban planning. While many works have been done for this purpose, it may be interesting to know which objects (terrain, buildings, trees, etc.) prevent other objects from being exposed to the sunlight. In this paper we propose a method which detects the sunlit zones on a city model and the shadow impact of its objects. As these objects can be of various natures and as the acquisition processes varies from one city to another, they are not all necessarily available in each city model. Since an object’s shadow can impact other very distant objects, we must have a method that handles efficiently large areas, especially knowing that city models can have fine geometric and semantic definitions. The generic approach we propose can manage these different city models by supporting every type of the above-mentioned objects and by relying on the use of standards. This paper presents a generic method which allows sunlight and shadow computation on arbitrarily large 3D city models for impact analyses of each city object on its surroundings (close and far). This means that besides checking if a city object is shaded or not, we know which objects are responsible for the shade, thus allowing various impact analyses on cities.