This material has been put together from a variety of sources, including mental images tutorials by Zap Andersson and Paolo Berto, images and movies showing skin layers from Barry Dempsey, and an image and mi file example for physical SSS from Dominika Waclawiak.

Downloads

• From Alias for Maya6 only (user community registration required).
  Do not load if you have Maya6.5, as it is now included.
  • Subsurface Scattering with Bonus Tools
• It comes included with 3ds max 7
• Other downloads will be announced when available.

Subsurface scattering requires mental ray 3.3 or higher.

Image courtesy Dominika Waclawiak

General

Subsurface scattering is a term used in computer graphics to describe the method for attaining the 'softer' look of natural materials such as skin, marble, and milk. The term comes from medical and light science. It means that light coming into the material scatters around below the surface, and then comes out again. It may be useful to know that even tiny amounts of scattering can enhance the apparent ''softness'' of a surface.

mental images provides two kinds of shaders for subsurface scattering. One approach implements subsurface scattering with volume scattering -- a physically correct simulation of the light scattering underneath the surface. The second approach does not use volumetric scattering at all, but rather simulates its appearance using light maps in a layered approach. This provides for a faster, easier-to-control method for achieving the SSS effect, and is especially tailored for rendering human skin.

Each approach has its unique strength regarding the tradeoff of desired visual effect and performance. For example, the physical approach uses photon tracing and handles the ability to pass caustics through the medium using the SSS material. It handles deeper SSS effects. Whereas, the non-physical approach doesn't require photon tracing, and handles shallower softening effects such as skin, leaves, grass, wax, plastic, etc. The information in the following sections should help you understand which approach is right for your project.

Includes concepts, and usage tips.

Includes concepts, skin models, and layered breakdown.

Includes diagrams depicting how the shaders for SSS are connected, along with .mi scene file examples. Phenomena (predefined shader combinations) come with the SSS shaders to simplify usage. Although they are documented in a section of the mental images shader documentation, each 3D application vendor may choose to slightly alter these Phenomena, to better fit their package, as is the case with Maya.