**Abstract**

The design of solar systems on the surfaces of buildings is based on an integrated approach to modeling: the duration of irradiation, zones of effective irradiation, shading zones, and angles of incidence of sunlight on the surface. In this case, the determining factor is the formation of methods for modeling the dynamics of changes in natural light. The conditions for natural exposure of surfaces are determined by the variable exposure to direct sunlight, scattered (diffuse) light, and complex light from the sky and the Sun. Each of these types of light has its own nature of changes presented in the study by means of geometric modeling. The authors proposed to bring together the methods of modeling variables of direct and diffuse sunlight by representing diffuse light in a ray form, that is, light vectors with variable parameters. This made it possible to simulate a rather complex combined effect of direct and diffuse light in solving problems of effective integration of solar systems on the surface of buildings.

**Keywords:** natural illumination, light vector, brightness of the sky, diffused light of the sky, direct sunlight, total light of the sun and the sky, heliosystems
