The lighting models described thus far have been relatively simple. The subtleties of real lighting are often captured using a global illumination model. Global illumination models using radiosity or ray tracing are generally too computationally complex to perform in real-time. However, if the objects and light sources comprising the environment are static it is possible to perform the global illumination calculations as a preprocessing step and then display the results interactively. Such an approach is both practical and useful for applications such as architectural walkthroughs. The technique is typically employed for diffuse illumination solutions since view-independent (ideal) diffuse illumination can be represented as a single value (color) at each object vertex.