Glass is one of the more easy materials to make because most of the work is done with the Refraction parameters and knowing the Index of Refraction (IOR) of the material you’re making (most fall between 1.3 – 1.6). Add something to the R.Glossiness to show use and you’re done. More complex glass, like mercury glass or bubble glass requires some work with masks and bump maps, but the processes are the same.
Rendering glass as solid or hollow depends on your geometry. If you’re making a table top or acrylic base the geometry should have a solid interior. Drinkware or a lamp shades have thin walls and are hollow so a Shell Modifier should be used. Solid and hollow glass refract light differently so it’s important you show it correctly.
An example of solid glass
An example of hollow glass
Next we’re going to make two types of common glass materials: Clear and tinted (tempered glass). The only difference between glass and plastic in both scenarios is the IOR and Refract/Glossiness amount (depending on plastic quality). Plastic, being a softer material, will show surface wear more than glass would, so bump maps and R.Glossiness maps would be slightly more noticable.
a. Clear Glass
Start with the Reflect color set a little less than all white and the R.Gloss high (.98). Add a grunge map to the R.Gloss slot and set it’s strength to 10. We want the effect to be subtle and just enough to break up the highlights. Fresnel Reflection values stay on and locked at the defaults.
Your Refract color is going to be close to pure white. This is controlling how transparent the object is, and also the color of the glass if needed. Glossiness is controlling the clarity of the refraction and IOR is controlling how the light bends as it passes through (effectively distorting the background). So for glass we’ll put the IOR at 1.54, and the Glossiness at .98 to get the look of quality glass.
Adding a scaled procedural noise to the bump map with a low value will give the glass that subtle imperfection in the refractions and add to the overall realism in the material.
b. Tinted Glass
The accurate way to colorize a glass material is by using Fog Color because it renders the thinner parts lighter and thicker parts darker. Fog Multiplier changes the strength of the tint whereas in Fog Bias negative values make the thin parts of the objects more transparent and the thicker parts more opaque and vice-versa (positive numbers make thinner parts more opaque and thicker parts more transparent). You can use Refract Color to colorize glass using bitmaps or procedurals for less accurate results.
c. Frosted Glass
To make frosted glass, the Refract Glossiness would be around .5 and the R.Glossiness would be .6 to blur the refraction but still allow light through. But experiment with different values to achieve the look you need.
d. Refraction IOR
While not a specific glass type, the image below shows the effects of changing the refraction IOR. A higher number will bend light more, causing the image through the glass to be more distorted and bent.