A 3D stochastic model of broken cloud geometry is constructed; it is adjusted according to satellite or ground-based observations. The model input parameters are an autocorrelation function of the cloud indicator field and a distribution of cloud layer thickness. A numerical algorithm is constructed based on spectral models of homogeneous random fields and on the method of nonlinear transformation of Gaussian functions. The proposed approach to broken clouds modeling is quite simple, universal, and makes it possible to reproduce key characteristics of cloud field geometry, estimated according to field measurements.