Absorption Medium

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.

AbsorptionMedium_Figure01

Figure 1: Specifying a blue hue in the Absorption parameter absorbs blue more quickly, thus giving the object an orange appearance

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.