The thermal infrared radiance simulation with aggregation modeling (TITAN) model, presented here, is an innovative transfer radiative code in the infrared domain (3-14 microm). It takes into account the three-dimensional (3D) structure of the landscape and simulates all the radiative components introduced by this 3D structure, which are due to the reflection and emission of walls and sloping roofs. Examples are given to illustrate the new opportunities offered by TITAN over urban areas. First, a phenomenological study is conducted at four wavelengths analyzing the relative effect of all the radiative contributors to the total signal. The same analysis is performed at bottom of atmosphere, which reveals an error occurring when a flat assumption is made (between 1% and 5%). In a second example, the directional effects at sensor level are simulated and show that the radiative temperature can vary by up to 10 K.