In the laser processing of glass, a ~50-1000 μm-thick layer of glass is heated to a high temperature by the laser beam. Due to the shallow depth of this hot layer, the infrared emission and absorption spectra may deviate from the black-body spectra and can be influenced by the vibrational structure of the material. Real-time time-dependent density functional theory (rt-TDDFT) modeling of the thermal radiation by such hot layers allows us to calculate the emissivity and thus to evaluate the reliability of the measurements conducted with thermal cameras at specific wavelengths.