In the numerical analysis of the indoor thermal environment with windows through which solar radiation is incident, it requires much computational time to identify irradiated surfaces. This paper shows the fast algorithm to calculate the wall surface distribution of the solar radiation through the window using the CG technique for the purpose of a prediction of the indoor thermal environment. We developed the fast calculation method of the direct solar radiation using parallel images made by graphics hardware at high speed. The diffuse solar radiation can be calculated by applying PPM (Pyramid Projection Method) that is the fast calculation method of view factors. PPM that we developed before uses perspective CG images. The errors of this algorithm are mainly derived from digitization errors of digital images. It was verified that this algorithms had a possibility to become an effective tool for the analysis of the indoor thermal environments with solar radiation.
