More on my continuing study of lighting effects on objects in three dimensional space. Lambert's Law states that intensity of incoming light (a ray of light) is directly proportional to the orientation of the light to the point on a surface. Basically this means that we can scale reflected light (an hence color perceived by the user) by the cosine of the angle between the incoming light ray and the direction the point is facing (the vertex normal). A dot product can be calculated between the 2 vectors (light vector and surface normal) to calculate the cosine of the angle between the two. We can then scale the light intensity by this value. Of course our material of our surface (reflective properties) will determine what the final result will be.