Part III. Illumination

One of the most important aspects of rendering is lighting. Thus far, all of our objects have had a color that is entirely part of the mesh data, pulled from a uniform variable, or computed in an arbitrary way. This makes all of our objects look very flat and unrealistic.

Properly modeling the interaction between light and a surface is vital in creating a convincing world. Lighting defines how we see and understand shapes to a large degree. The lack of lighting is the reason why the objects we have used thus far look fairly flat. A curved surface appears curved to us because of how the light plays over the surface. The same goes for a flat surface.

Without this visual hinting, surfaces appear flat even when they are modeled with many triangles and yield a seemingly-curved polygonal mesh. A proper lighting model makes objects appear real. A poor or inconsistent lighting model shows the virtual world to be the forgery that it is.

This section of the book will cover lighting, using a variety of light/surface modelling techniques. It will cover dynamic range and linear colorspaces in lighting equations. Also, it will cover techniques to use lighting to produce entirely fake surfaces.