Lighting model
In 3D computer graphics, a lighting model is generally used to describe a process that simulates the behavior of light. Usually this means a local lighting model that simulates the surface of objects. Global lighting models, on the other hand, simulate the propagation of light within a scene , but this term is not widely used.
Local lighting models
Local lighting models simulate the behavior of light on surfaces. The brightness or color of a light beam reflected from a point on this surface in a certain direction is calculated. This is done with the exclusive help of the viewing direction, the angle of incidence of light, the material properties of the object and the light sources. The indirect lighting is initially not taken into account here. Global lighting models are responsible for simulating these effects; Ray tracing, for example, sends out additional rays for this purpose.
In contrast to other methods for representing a material such as bump mapping, lighting models do not simulate the mesostructure , but the microstructure of a material. Depending on the type of display, different shading methods must be used for this.
The most famous local lighting models are:
- Lambert lighting model (1760)
- Phong lighting model (1975)
- Blinn lighting model (1977)
- Torrance Sparrow lighting model (1967/1982)
Most local lighting models can be described mathematically as a bidirectional reflectance distribution function (BRDF).
Global lighting models
Global lighting models simulate the propagation of light in a scene. In general, this means radiosity or ray tracing or their variants. They are very computationally intensive and therefore, with today's state of the art, the sole method either not suitable for real-time rendering (ray tracing) or only for displaying static scenes that can be partially calculated in advance (radiosity). The term global lighting can refer to a global lighting model, but is often only applied to those global lighting models that take into account the propagation of all light rays in a scene.
literature
- James Foley et al. Computer Graphics: Principles and Practice, pp. 721-814. Addison-Wesley, Reading 1995, ISBN 0-201-84840-6