In order to support the conceptual design, the architect used throughout the years, mockups - scaled physical models - or perspective drawings that intended to predict architectural ambience before its effective construction. This paper studies the real time interactive visualization, focused on one of most important aspects inside building space: the natural light. Although the majority of physically-based algorithms currently existing was designed for the synthesis of static images which may not take into account how to rebuild the scene - in real time - when the user is doing experiments to change certain properties of design.