Conclusion

3D CG lights are much more flexible than real world lights so they can be used very creatively. The technique of adding bounce lights have been used since 3D CG is mature enough to produce images and films. Bounce lights are positioned, oriented and colored so they simulate indirect lighting that would come from surrounding objects. The technique of adding bounce lights can be finely tuned to get a desired natural effect as well as to obtain a desired dramatic effect. In 3D CG, bounce light may even have negative intensity, in which case, the light would ast shadows, so to speak. This is something that cannot be obtained in the real world.

Shadows are very important in a scene. Shadows sit each objects in their environment. Without shadows, it is very difficult, if not plainly impossible, for the viewer, to determine the spatial relationship between the objects and their environment. The most important shadows, should come from the natural lights in the scene. Bounce lights should not cast shadows or at least, they should only cast very diffuse shadows. Shadows should be believable too. Our visual system have developped so the interpretation of shadows give us important visual cues about the real world. Incorrect shadows, such as too soft shadows or missing shadows will unmistakenly give the CG origin of the image. Improper shadow settings can also produce pervert effects such as light seemingly shining from inside the character's mouth or nose or ears.

Lighting and shadows are just two important aspect of believable renders though. The models used must also be modeled and textured in a believable way and the environment must be populated in a believable way with believable objects. The thanksgiving dinner scene we used for this tutorial can only be really pushed this far. To push it further in realism and believability would require that a lot of additional objects be placed in the scene. More objects on the table, on the floor and on the walls. Dressing the window with curtains and blinds for instance. A less neat and regular organisation of the objects on the table. Some variation in the chair positions. Stuff like that. Attention to details when preparing textures is important. Scratches and dirt spots are important visual clues that should be overlooked. No amount of attention to lighting and shadows can really push the realism of a scene is the scene itself looks artificial.

And last but extremely important, every 3D CG render should be tone corrected before publishing. The direct output from a renderer is unsuitable for publishing because the lights that comes out from the renderer is computed in a linear space. This is physically correct but just like every photo out of digital cameras are tone corrected, the renders should also be tone corrected to compensate for the non-linear characteristics of computer monitors.