 The rendering equation doesn't account for all lighting phenomena, but instead acts as a general lighting model for computer-generated imagery.In the case of 3D graphics, scenes can be pre-rendered or generated in realtime.Pre-rendering is a slow, computationally intensive process that is typically used for movie creation, where scenes can be generated ahead of time, while real-time rendering is often done for 3D video games and other applications that must dynamically create scenes.