The following attributes are needed for subsurface scattering simulations. Note that the reduced absorption and reduced scattering coefficients and refraction index are usually obtained from specialized literature. The 3Delight-UserManual.pdf contains a discussion about this topic and a reference to surface properties directly usable by 3Delight.
Subsurface Group
This attribute specifies a group name. Objects that have the same group name will belong to the same subsurface group. If the object that will undergo the subsurface simulation consists of several separate models, each of these models should be attached to a Geometry Attribute Node and this attribute should be assigned the same value in all of these nodes. Even if a model is closed and thus would be alone in its group, it is still required to specify a group name here. This attribute is empty by default. Leaving this attribute empty effectively turns off subsurface scattering.
Reduced Absorption
Specifies the reduced absorption coefficients. Its default value is ‘0.002 0.004 0.007’.
Reduced Scattering
Specifies the reduced scattering coefficients. Its default value is ‘2.190 2.620 3.00’.
Refraction Index
Specifies the refraction index of the simulated material. It is set to ‘1.5’ by default.
Coefficient Scale
The values for subsurface scattering use a millimeter scale. This attribute specifies the scale to apply these parameters when the objects are not exported in millimeters. The default value for this attribute is ‘0.1’, since 3Delight for Maya exports the objects in centimeters.
Subsurface Shading Rate
Specifies the shading rate used for the subsurface simulation. Its default value is ‘1.0’.