Abstract The architectural and urban design project is a complex work (artistic and legislative, aesthetic and cultural, technical and sensible, etc.). In this research, we present a numerical tool and its applications that enable to take into account the ambient environment factors during the architectural and urban design process. Generally, solar or visual "direct" simulation allows analysing a situation at a given instant or for a given point of view. In architectural and urban spaces, our "inverse" approach solves problems of sunlighting, visibility and solar reflection in built environment. By applying the principles of inverse simulation, our numerical model enables to mix these parameters and proposes to consider the relation between a base (given observer positions or a solar area) and a target (solar period – part of the sky vault – or visual element like, monument, landmark, etc.). This relation represents a volumetric constraint. The CAD tool that is developed (SVR software) helps the designers to display architectural and urban constraints and also better to take into account solar and visual impact of urban projects. Our model enables to find solutions in order to satisfy these solar and visual constraints and to generate and manipulate geometrical volumes (3D solids) such as other architectural objects or urban blocks, with AutoCADs software. These solutions of the calculations are "volumes of solar or visual constraints". They represent the whole of the sunbeams or visual rays between the base and the target. Such a representation enables architects and urban planners to find the exact solutions of a given constraint, and to conceive more sustainable devices in the long-term. We observed eleven architects or students in architecture, which used our software prototype during sketches and draught phases of architectural design process. For analyse these designers, we have used the "think aloud" protocol.