Cornell University Program of Computer Graphics
This sculpture can be used to illustrate why modeling direct light reflections alone cannot replicate all natural light effects for computer graphics imagery.
A diagram drawn looking down on the sculpture shows that the colored surfaces face away from the viewer (who looks from the bottom of the diagram), but are bathed in light from a strong light source (at the top of the diagram). Only white surfaces face the viewer.
A ray-traced version of the image shows only the light reaching the viewer by direct reflection -- hence misses the color effects.
This image, incorporating radiosity techniques for image generation, correctly models light reflections from diffuse surfaces, and captures the strong color effects that the sculptor intended.