Reference: https://www.dgp.toronto.edu/~karan/courses/csc418/fall_2002/notes/illum_local.html

1. Local Illumination

   → Defines single-light, single-surface interaction

   <aside> 💫 I = ambient + diffuse + specular

   

   </aside>

   • Ambient term allows for some global control of brightness in a scene.
   • Diffuse is when light reflects off of a surface in all directions. This is opposed to specular reflection, which is when light reflects off of a surface in a single direction. Diffuse reflection is what gives surfaces their matte appearance.
   • Specular:

   <aside> 💫 The Phong Illumination Model is one often-used method of calculating the specular component:

   

    Is = Ii * k_spec * cos^n (alpha)
       = Ii * K_spec * (R.V)^n
   

   where

   • k_spec: a specular reflection coefficient
   • alpha: angle between the reflection and viewing vector
   • surface parameter 'n' can be thought of as describing the surface roughness, where an ideal mirror would have n=¥ , and a rough surface might have n=1. </aside>

2. Global Illumination

   → Models interchange of lights between all surfaces