Optical system modeling is interdisciplinary by its very nature. Optics, thermal engineering, structural engineering, control systems, electrical engineering, and data analysis are among the disciplines required to perform such modeling. Each discipline tends to have various software tools at its disposal to perform the required design and analysis but the software tools have had only limited ability for interdisciplinary use. Optical design software can form the core for optical systems modeling in many instances but its capabilities must be extended, or it needs to be used in a non-traditional way, depending on the problem at hand. We have used optical design software to assist in or form the basis for solving a number of interdisciplinary optical systems modeling problems. As an example, we present our method of dynamic optical ray tracing here and show its application. We also mention an example of linking optical design software to external code to solve optical systems modeling problems. Although these modeling efforts were successful, they illustrate the associated difficulty and need for integrated software modeling tools.