Summary of 3 Illumination Models

Illumination models take into account each individual point on a surface and the light sources that are directly illuminating it.

Ambient Reflection

Ambient reflection is the result of inter-reflection from the walls and objects. However, it is modelled as a constant term for the specific object, such that a 3D sphere looks 2D. This approximates diffuse reflection globally.


Spheres shaded showing variation of magnitude in ambient component over the surface of each sphere. From left to right, increasing amount of cyan ambient reflection.

Diffuse Reflection

Most objects around us do not emit light of their own. Rather they absorb daylight, or light emitted from an artificial source, and reflect part of it. Here, light that reached the surfaces would be scattered equally in all directions. This implies that the amount of light as observed by the viewer is independent of the viewer's location.

Spheres shaded showing variation of magnitude in diffuse component over the surface of each sphere. From left to right, increasing amount of cyan diffuse reflection.

Specular Reflection

Many real world surfaces are glossy, such that when viewed from certain angles they can be seen reflecting light. A glossy surface reflects a high proportion of light, while the rest is the result of diffuse reflection. This glossy or shiny reflection is called specular reflection.

Spheres shaded showing variation of magnitude in specular component over the surface of each sphere. From left to right, increasing amount of specular reflection.