| The sky is an important background for an Infrared imaging system (IRIS) when detecting targets in the sky. Therefore the study of the infrared radiation properties is of great need.The clear and the cloudy sky are studied in this paper, respectively. For the clear sky, its 3-D simulation scene is mapped from the hemispherical sky dome and its texture, which is established through the atmospheric radiation computed by MODTRAN. For the cloudy sky, the background refers to the 2-D cloud which is created by fractal algorithm, and its radiation is gained by the statistical analysis of the real infrared cloud radiation. The 3-D cloud of the cloudy sky is created through the particle system, and its radiation is obtained by grey body approximation. The 3-D visual model of the sky is set up utilizing Direct3D and the results of the simulation in different conditions are analyzed. |
