Real-time mid-wavelength infrared scene rendering with a feasible BRDF model

Practically modeling and rendering the surface-leaving radiance of large-scale scenes in mid-wavelength infrared (MWIR) is an important feature of Battlefield Environment Simulation (BES). Since radiation transfer in realistic scenes is complex, it is difficult to develop real-time simulations directly from first principle. Nevertheless, it is crucial to minimize distortions in the rendering of virtual scenes. This paper proposes a feasible bidirectional reflectance distribution function (BRDF) model to deal with a large-scale scene in the MWIR band. Our BRDF model is spectrally dependent and evolved from previous BRDFs, and meets both Helmholtz reciprocity and energy conservation. We employ our BRDF model to calculate the direct solar and sky contributions. Both of them are added to the surface thermal emission in order to give the surface-leaving radiance. Atmospheric path radiance and transmission are pre-calculated to speed up the programming for rendering large scale scenes. Quantitative and qualitative comparisons with MWIR field data are made to assess the render results of our proposed method.