9. Diffuse lighting, cont.

If vectors L and N are normalised, cos(a) is the dot product:

• cos(a) = L·N

The diffuse intensity Id is computed by adding the diffuse component of the object's material, Kd:

• Id = Kd * L·N

In practice, we need to avoid negative L·N values:

• Id = Kd * max( L·N, 0 )

Also, we can now easily add ambient light Ia to the result:

• Id = max(
           Kd * max( L·N, 0 ),
           Ia
          )

where Ia is the ambient light intensity.

L – the incoming light vector

N – the normal of the plane/vertex