A novel method for pairing surface irradiation and volumetric absorption from ray tracing to computational heat transfer models is presented. The method is well-suited to directionally and spatially-complex concentrated radiative inputs, such as in solar receivers and reactors. The method employs a generalized algorithm for directly mapping absorbed rays from the ray tracing model to boundary or volumetric source terms in the computational mesh. The algorithm is compatible with unstructured, two and three-dimensional meshes with varying element shapes. To validate the method, four case studies were performed on a directly irradiated, windowed solar thermochemical reactor model. The method was shown to be energy conservative and to preserve spatial variation when mapping rays from a Monte Carlo ray tracing model to the computational heat transfer model in ANSYS Fluent.