The image below illustrates a simple scene as it appears when rendered in 3DStudio Max animation software.

It is lit with four spotlights shining down directly from above. This rendering algorithm determines the illumination of a surface by examining the angle of incidence of the light onto the surface.

While the floor looks fairly believable, notice that the

walls (which are actually a neutral beige) appear as black or dark gray. This is because the light from the spot lights is striking the walls at an oblique angle. Also notice that the shadow areas are pure black. In conventional rendering the effect of light bouncing off of surfaces is not taken into account. Since no light is directly striking these surfaces they are rendered black.

The overall effect is obviously not very realistic.