Infrared ship signature prediction using measured BRDF data and global illumination rendering

Current IR ship signature codes have some limitations in predicting ship IR signatures. They either model general BRDF while ignoring multi-reflections, or compute multi-reflections with simplified BRDF models. We propose a new Monte Carlo ray tracing method incorporating measured BRDF data, which can calculate multi-reflections with general BRDF data. Much works have been done in computer graphics to simulate light transport for global illumination. In order to apply the global illumination algorithm in infrared ship signature prediction, we have modified the global rendering algorithm to include some important features like validation of physically accuracy, capability of incorporating measured BRDF data into the rendering equation, environment modeling of sky and sea radiance distribution and modeling surface patch as both reflector and emitter. The validation of physical accuracy performed by comparing the analytically calculated value with global illumination based infrared simulation result. The measured BRDF data is interpolated and used in the recursive Monte Carlo ray tracing. The environment and surface emissivity modeling can benefit from the physically based sky and sea radiance simulation as well as the thermal simulation result.