Absorption

AbsorptionDefines how fast light is absorbed while passing through a medium. means that the material slightly absorbs light while passing through. The color resulting from this absorption is dependent on the distance light travels through the material. With increased distance it will get lighter, and if the absorption is colored it will get more desaturated. It works in a subtractive way, so you need to configure the inverted colour instead to get an absorption colour desired.

Absorption Parameters:

Absorption - Controlled by Absorption color, which defines how fast a medium absorbs light passing through it. A 0.0 or black value means no absorption. Higher values result in faster light absorption. The specified color in the Absorption parameter produces its complimentary color in the rendering (Figure 1). The Absorption texture is multiplied by the Density parameter. This allows setting a wide range of values.

Volume Step Length - Depending on the surface, you may need to adjust this parameter. The default value is 4, but if the volume is smaller than this, you need to decrease the Step Length. Decreasing this value decreases render speed, and increasing the value causes the ray marching algorithm to take longer steps. If the Step Length exceeds the volume's dimensions, then the ray marching algorithm takes a single step through the whole volume. To get the most accurate results, keep the Step Length as small as possible.

Invert Absorption - Inverts the Absorption color so that the Absorption channel becomes a Transparency channel. This helps visualize the effect of the specified color, since a neutral background shining through the medium appears in that approximate color.

Figure 1: Specifying a blue hue in the Absorption parameter absorbs blue more quickly, thus giving the object an orange appearance. The object on the left has no absorption medium, the object in the middle has ‘Invert absorption’ disabled and object on the right has ‘Invert absorption’ enabled.

Figure 2: The parameters on the left show the Reflection and TransmissionA surface characteristic that determines if light may pass through a surface volume. setting for all object in the previous example. The parameters on the right show the Absorption setting for the objects in the middle.

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