For more details about SolTrace's capabilities, see the SolTrace website. The creation of the code evolved out of a need to model more complex solar optical systems than could be modeled with existing tools. Although ideally suited for solar applications, the code can also be used to model and characterize many general optical systems. SolTrace is a software tool developed at NREL to model concentrating solar power (CSP) systems and analyze their optical performance. The SolTrace Open Source Project repository contains the source code, tools, and instructions to build a desktop version of the National Renewable Energy Laboratory's SolTrace.