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Created a gemstone using boolean and difference. The material is GlassBSDF (Green Cubic Zirconia). I have tried all the lamps and emmiting planes in a number of configurations and cannot achieve a realistic gemstone.

I tried a sky background and my clear gemstone became a blue gemstone. The best results so far is with a background that is Gradient and Radial. The gemstone has distinct facets. It should be symetrical about the X and Y axes but it is not because of the gradient.

I tried a RGB background but the facets were not distimct like I get using a Gradient background.

What do I need to do to achieve a gemstone with distinct facets on a White background?

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    $\begingroup$ A good HDR might give satisfying results. $\endgroup$
    – GiantCowFilms
    Commented Feb 18, 2016 at 16:28
  • $\begingroup$ Making realistic scene involves many aspects (light, shaders, camera settings...). If you could provide an image of your best result and the reference images it would be easier to tell what is your setup lacking of. Related question: blender.stackexchange.com/questions/40226/… $\endgroup$
    – Carlo
    Commented Feb 18, 2016 at 16:36
  • $\begingroup$ The issue you are dealing with, I believe, is whether or not the facets of the gem refract light correctly. A well-cut gemstone refracts 100% of light back to the viewer's eye, and hence has a perfect cut. In this picture the "Ideal Proportions" cut shows 100% perfect refraction of light. However, a poorly cut get's facets do not refract light back to the viewer's eye, as shown in the "Shallow" and "Deep" cuts -- this effect is known as "Windowing". Here is a good example picture of a large window. I don't know if Blender supports refraction. $\endgroup$
    – Thom Blair III
    Commented Feb 18, 2016 at 16:55
  • $\begingroup$ As an aside, a green cubic zirconia (CZ) will have some browns and possibly other unwanted colors in it due to CZ's dispersion (fire) properties. As a result, CZ, in my opinion, is a poor choice substitute for an emerald--emeralds only show green to the viewer's eye, not the other, wider dispersion spectrum of CZ (which then gets brown muddy colors caused by the reds and oranges mixing with the green doping of the CZ's dispersion) $\endgroup$
    – Thom Blair III
    Commented Feb 18, 2016 at 17:04
  • $\begingroup$ Also, note that when modeling cut gemstones, it is the crystal structure of the molecules that determines the dispersion/fire (colors of the stone), and it is the cut (angles of the facets) that determines whether or not the cut gemstone will reflect light back to the viewer's eye. If you are trying to get an extremely accurate model specifically of green Cubic Zirconia, then you will have to take these into consideration. $\endgroup$
    – Thom Blair III
    Commented Feb 18, 2016 at 17:11

3 Answers 3

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If you're not, then you should probably use the cycles render engine.

Try using a simple studio hdri environment texture, combined with additional lamps.

I would also suggest bevelling the edges for even more realism

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If you don't mind cranking up your render times try using volumes to create density or simulate it with translucency or SSS. Also make sure to use something like a noise map as surface displacement and have it also effect the roughness to simulate surface weathering.

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Finished Result:

(It's a little noisy, sorry about that).

enter image description here

Explanation:

Any gem that you'd find out in nature will have tons of different particles inside of it. Luckily, we can fake that by using Fresnel, Volumetrics, Emissions, and a little bit of Subsurface Scattering (SSS). Note that a little bit of Node Editor experience is recommended.

How It's Done:

We're going to start with the simple color and looks that a perfectly-clean gem would have. I used a Mix Shader node to combine a Diffuse & Glossy (with a roughness of 0.2) Shader with a Fresnel (with a IOR of 1.450) into the Factor input, with another Mix Shader (0.95 Factor) to combine the output of the previous Mix Shader with a Glass Shader (with a roughness of 0.050). Repeating the last step, I plugged in an Emission Shader (with a strength of 1) to the following Mix Shader (Factor 0.005). By plugging that into another Mix Shader, I added a Subsurface Scattering node (with a scale of 1) into the input and another Fresnel node (with an IOR of 1.450) in the Factor input. After connecting the last Mix Shader to the Surface input of the Material Output, I added in a Volume Scatter node. What this will do is fake all of the particles that are inside of the gem. I used a density of 1 with a white color, but you can tweak it to make it look more foggy or dirty. Don't forget to plug that into the Volume input of the Material Output when you're done. Here's a picture:

enter image description here

Experiment!

Now that you've got everything set-up, go ahead and experiment with it! Add surface imperfections (achieved by adding an Add Shader to the last Mix Node and plugging in an Image Texture with a Surface Imperfection picture), such as dirt, scratches, smudges, or even cracks! If you wanted to get real fancy, add in some bump map to those imperfections. I also recommend you tweaking with the roughness of the Shaders and the Factors of the Mix Shaders. I won't go any further into depth here, it's all just personal preference.

Download the Example Blender File:

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