Abstract: Currently existing 3D cloud simulation illumination models were confronted with the shortcomings such as complexity of implementation and low rendering efficiency. Herein a calculation method for illumination model based on importance sampling was proposed; Aiming at the problems of the old phase function, a new phase function was proposed to improve the rendering efficiency and quality. By the design of the importance function, the method did importance sampling in integrated interval and combined two phase functions to render the cloud. The results of the simulation show that the presented method has enhanced the rendering speed with the guarantee of rendering quality. The result of the visualization can display the physical characters of the cloud both in rendering efficiency and quality, ensuring perfect visual effect.

Key words: illumination model, phase function, importance sampling, multiple scattering, three dimensional cloud rendering