Credits: Thomas Anagnostou
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This parameter controls the color of the light when it passes through a transparent material. Choose a Transmittance color by clicking on the color picker, or specify a texture by clicking on the texture button. The Transmittance color represents the color of the light when it has reached the Attenuation distance (see below).
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Transmittance must be a color other than black for transparency to appear. Setting a brighter transmittance color results in clearer transparency, but you should remember that this parameter is also tied to the Attenuation Distance. |
Attenuation
Glass, water, or even air are transparent when thin, but become opaque when a specific thickness is reached (different for each material). This is because as light travels through a material, it loses energy. The Attenuation distance parameter allows you to specify how far light can move through an object before losing half its energy. For example, if you have a 2cm thick glass window and you set the attenuation distance to 2cm, the light shining through the glass on the other side will be half as bright.
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All parameters the same except roughness. Above: roughness 0, Left: roughness 50, Right: roughness 50 with changed reflectance colors
Abbe (dispersion)
Different wavelengths of light can be refracted at slightly different angles as they pass through a material, and this is what causes dispersion, the effect seen when a beam of light passes through a prism and is split up into the different wavelengths of light.
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Glass material with Dispersion calculations disabled (left) and enabled (right)
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Dispersion must be enabled in the global Material Properties panel; otherwise the Abbe parameter in the BSDF will be greyed-out. Because dispersion generally takes longer to render, it is disabled by default. See the Global Material Properties section. |
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