Constant or Flat Shading

One illumination calculation for each facet/polygon

The simplest shading method applies only one illumination calculation for each primitive. This technique is called constant or flat shading. It is often used on polygonal primitives.

Computation done at the centroid

Illumination is computed for only a single point on the facet. Which one? Usually the centroid. For a convex facet the centriod is given as follows:


For point light sources the direction to the light source varies over the facet

For specular reflections the direction to the eye varies over the facet