Transparent material is used for all materials where most of the light go through the material (refracted) without any scattering, but with some degree color absorption.
Typical examples are glass, water, acrylic, quartz, diamond, ruby, and emerald.
 Light grey glass |
 Light Red glass |
 Heavy Red glass |
 Emerald |
Light inside the material travels in a straight line, but can be affected by the entry and exit surfaces as they can be rough like in a frosted glass.
The absorption is the apparent color of the interior of the material, and is always associated with a specific distance. The further the light travels inside the material the darker the color will become.
Using the Roughness parameter, you can achieve a frosted glass look.
 Lightly frosted glass |
 Frosted glass |
Transparent Material Specific Parameters
- Color and Absorption Distance
- The color of the transmitted light at the specific Absorption Distance.
- A glass sheet the same thickness as the Absorption Distance would transmit a light colored as the specified Color. A sheet twice as thick would transmit a darker shade of the same color. A sheet half as thick would transmit a lighter shade of the color.
- On a solid volume, like a vase or a statue, the light will assume darker or lighter shades of the color depending how much it travels through the volume before exiting.
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Sheets of glass of different thickness
A colored glass with variable thickness
- Index of Refraction
- The index of refraction (IOR) indicates how much the light bends when entering a material of a different density. The bigger the difference, the more the light bends.
- Air, which is commonly the material surrounding a scene, is assumed to have an IOR of 1.0. Any transparent material is denser that air and will have a higher IOR.
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Water
Glass
Diamond
- Water, with an IOR of 1.33, will bend the light less than Diamond, with an IOR of 2.4. Materials with a lower IOR also reflect less than ones with higher IOR, as visible from the samples above.
- Her are examples of IOR for some common materials:
Material
IOR
Air
1
Water
1.333
Glass (Optical)
1.54
Quartz
1.545
Diamond
2.419
Polycarbonate
1.585
Acrylic
1.491
Plastic
1.46
Glass (Silica)
1.459
Plexiglas
1.488
Glass (Pyrex)
1.474
Glass
1.52
Emerald
1.57
Ruby
1.77
Sapphire
1.77
Crystal
2