As this site has developed, I have received questions on how to get the gem models to render with all the sparkle and flash of the real thing. This section will deal with the means necessary to adjust the models, it's materials and it's environment in order to create a gem of an image.

STEPS TO IMPROVING YOUR GEMSTONE RENDERS.
1. UNSMOOTHING THE MODEL
2. ADJUSTING THE MODEL TO FIT THE IOR
3. CREATING THE ENVIRONMENT
(more sections to come as time allows)

 

STEP 3. CREATING THE ENVIRONMENT

There are two main environments that most artists will be concerned with; a 'natural' environment (where the gems may be laying in a treasure chest, or hanging in a necklace around a person's neck, thus just one object among many), and what I call a 'showcase' environment (where the gems are the only items in the scene, and are the primary focus of the image).

---------------

For the first type (natural environment), I can offer only a few suggestions, since positioning of objects and their lighting depend on the artist's own choices.

1. Many rendering programs allow for lighting, and shadows, that can be turned off for individual items. This allows for an improved control over which objects get the viewers' attention. Sometimes a tiny spotlight that only lights up one gem can vastly improve it's visibility in a scene.
2. Remember that the surrounding objects will be both reflected and refracted by the optical qualities of the gem's material. Try to choose the level of both which gives the best 'look' to the gem and the image. If, for example, a striped object nearby is reflected too strongly on a gem's surface, you can 'turn down' the reflective settings for the gem. But doing so may decrease the sparkle that those refections provide.
3. Get critiques from your artistic peers while assembling the image. Often they can spot a 'fix' or suggest a technique that you haven't thought of.

--------------

For the second type ('showcase' environment), I can offer a few more suggestions, as most of the renders I have done up to now are of that type (thus giving me a bit more practice! LOL)

Here are some examples of to start setting up the environment.

		Here is a typical gemstone. The environment is very simple--a dark blue sky, with a black backdrop. There are three lights of varying strangths. The material is set as 'diamond'-100% transparent, refraction of 2.41, reflection of about 25%. The exact same setup is used in the second picture, with one major exception.
		Here I have added something for the gem's reflective qualities to work on--some free-floating white-colored squares surrounding the gem.
		Here is a side-view diagram of the setup. The gem is the green model, the yellow globes are the lights, the blue is the camera, and the red squares are the reflector panels. The squares create 5 sides of an open box around the model, and are out of sight of the camera's point of view.
The advantage to creating such a surrounding setup, is that when you make an animation, for example, the gem's different facets pick up the reflections at different times, thus creating unanticipated sparkles.

 

 

But what works for a single gemstone doesn't always work for a more complicated scene. Here are four examples of how differently a scene can look:
1. This is the same setup used for the single gems shown above-black backdrop, dark blue sky, white reflector panels. Note the gem looks good, but the metal of the ring clearly shows the shapes of the white panels. Also the metal is 'lost' in the surrounding black.		2. The same setup, minus the black backdrop. The ring stands out more, but still shows those white reflector panels in the metal.		3. Here both the black backdrop *and* the white reflector panels are gone. Instead, the sky is colored black, with a white ground plane which blurs off into a black haze. Both the ring and the gemstone show up well, but this is a rather boring version--let's do better!		4. In this version, I created an enormous sphere surrounding the entire scene: ring, camera, lights are all inside. On the sphere is a mottled texture map--(some people use an actual environmental picture to add to the realism). This creates a much more interesting and believable picture. Both the ring and gem show up well.

To sum up the above tips:

Remember that your model *lives* in an environment. If you give the gem refractive and reflective material settings, make sure to also give them something for those qualities to work on. If you can't actually 'build' an entire surrounding world, put in enough 'stuff' around to help out. Those default grey backgrounds that many 3d applications give you don't give the best renders of a gem.