室外场景的光照模拟与图象合成的难点在于场景与光照的复杂性。提出了一种利用现有基图象的线性组合来生成不同天候条件下同一场景图象的方法。它根据光照函数的线性关系，估计不同太阳位置和不同天气状况基图象的系数，从而最终通过基图象的组合来产生目标图象。实验结果表明本文的方法用于固定场景下的图象合成是可行的。

Lighting simulation and image synthesis for outdoor scenes is intractable due to the geometric and lighting complexity of such environment. In this paper we present an efficient solution to the problem of image synthesis by linear combination of acquired basis images. According as to the linearity of illumination function, the coefficients of basis images of varying sun position and sky conditions can be calculated to generate the desired image. Our method has been proved suitable for fixed scene and camera geometry.