Advanced material models for dispersive, nonlinear and gain modeling using finite-difference time-domain (FDTD) methods are challenging due to the diversity of problems to be solved. A nonlinear model may be as simple as an instantaneous χ(2) or χ(3) effect, or may involve additional dispersive and anisotropic nonlinear terms. While it is relatively straightforward to provide a particular nonlinear material model appropriate for a specific application, it is a challenge to provide the wide range of different nonlinear material models that are required. In addition, it can be challenging to combine nonlinear responses with linear dispersion, which can be critical when considering issues such as phase matching.