Abstract: Systems and methods which provide modeling or simulation of gamma ray (GR) tool response using a hybrid analytical and numerical technique are shown. Embodiments employ a GR tool simulation technique which provides gamma ray information simulated as a function of only the gamma particles which reach the detector without scattering. Embodiments utilize a discretization function to determine the gamma particles which would reach a point detector from each unit volume source of an investigation domain without scattering. Embodiments further utilize the foregoing discretization function with respect to a plurality of point detectors, wherein the particular number and configuration of point detectors are selected to relatively accurately simulate the results of a particular GR detector configuration, such as line detector or volume detector configurations.