Graphics Reference
In-Depth Information
Figure 2-81
The SSS panel
RGB Radius
R,G,andBaretheblurringradiiforRed,Green,andBlue.Thesevaluesdeterminethedistance
thatdifferent-coloredlightscattersunderthesurfaceofthematerial.Ifyou'veevershoneaflashlightthrough
your hand in the dark, you have seen that the red in your hand scatters more than the other colors.
IOR
IOR is the index of refraction, or the degree to which light is bent when it travels through the material.
As mentioned in the previous section, higher IOR values indicate higher density. In the case of subsurface
scattering, the effect is subtle, because no actual rays pass through the material. In most cases, you can get
away with setting the IOR to approximately the value of water, 1.3.
Error
Error controls the precision of sampling. Higher error values will speed up rendering but can result in
visible artifacts. You can set it as low as 0.02.
Color
Color determines how much the base color of the material is affected by the subsurface scattering ef-
fect.
Texture
Texture controls the degree to which textures on the material are also blurred; 0 will leave the tex-
tures unaffected by the scattering.
Front
Front is the weighting factor for front scattering. Front here means pointing toward the camera. Front
scattering shows as diffusing of the light and blurring of the shadows on the surface of the material.
Back
Backistheweightingfactorforbackscattering.Backscatteringshowsupaslightpassingthroughfrom
behind the material.
Figure 2-82
shows three objects with materials that differ only in their subsurface scattering. The image is
reproducedinthecolorinsertofthebook.TheknightonthelefthasnoSSS,theknightinthemiddlehasstrong
front SSS with weaker back SSS, and the knight on the right has strong back SSS with weak front SSS. Of
course, for more-convincing materials, you would also want to adjust the shader values appropriately; wax has
a different specularity than jade, for instance. This example is mainly to highlight the differences in the subsur-
face scattering effect itself.
