A high-fidelity numerical model is developed for the incoherent electro-optical imaging process in media where the inherent optical properties vary with range. Four contributions to the image data are considered: laser light reflected from the scene, volume backscatter of laser light, reflected solar light, and solar backscatter. The model implements rigorous mathematical formulations, incorporates adaptive error control, uses computationally efficient algorithms, and has been rigorously validated. The model is flexible enough to handle many different sensor configurations and sampling techniques, continuous-wave and pulsed laser sources, and range-dependent properties of the optical environment. The derivation of relevant mathematical models is reviewed and unified into a comprehensive and flexible system that can be tailored to fit the various incoherent electro-optical imaging systems currently in use or in development. The numerical implementations are described for each key component of the overall model, and a sampling of new verification and validation results is provided.