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Image courtesy of Toni Fresnedo (www.tonifresnedo.com)
Introduction
To create a transparent material in Maxwell you must first set the surface roughness (see Surface Properties) low enough for a typical clear transparent material (roughness 0 - 5) or rough glass (5-25), and then use:
the parameters Transmittance and Attenuation to control the color and transparency of the material.
the ND parameter to control the index of refraction of the material. A list of typical refractive values can be found here
the Abbe parameter if you also want to render dispersion effects (see below)
Transmittance
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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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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