Three-dimensional longwave infrared synthetic image generation incorporating angular emissivity effects using ray-tracing techniques

A technique for longwave infrared (LWIR) synthetic image generation is shown which yields improved radiometric accuracy in the 8-14 micron bandpass. This process uses a modified LOWTRAN 6 atmospheric transmission/upwelled radiance code and computer graphics ray-tracing techniques. A scene is created by placing faceted objects into world coordinates with rotation, translation, and scaling parameters. Each facet is assigned a material index and temperature. The material index points to optical properties for that material. The modified LOWTRAN 6 code incorporates sensor response function when computing tables of the atmospheric transmission and upwelled and downwelled radiances. A ray-traced image is then generated. A final synthetic LWIR scene is generated to geometrically match an actual acquired scene so that radiometric comparisons can be made.