The purpose of this study was to express a system with real-time modeling and rending of skies and clouds for an emotional online game. Especially, it was suggested that the method was processed with modeling data by the real time through evaluation of the character’s emotions. The colors of skies and clouds were happened to emotion-based automatic generation, which was intended to a way of game players. Generating the clouds was used with the random course system and the density of clouds was made with indexing values of generating time. From the applying light in-scattering effects to the volume photon mapping technique, it was preset using the index value, which was generated with the efficient processing performance. Consequently, it was improved the performance about storing and searching, the fastest rendering processing efficiency, and generating on pictures of high quality in very fast time by using the KD-tree.