My SSS objects are faceted!

1. Why objects are faceted

You may sometimes notice that certain objects with SSS (volumetric) materials applied are visibly faceted. Although the result may appear incorrect, it is not really a bug or an error - this is exactly how the object is expected to look when rendered.

[See material settings]

The reason of this is that any geometry in most 3D applications really is faceted. We are not used to seeing the faceting on an object's surface thanks to shading normals, which are used to "fake" the smooth appearance of 3D surfaces. The shading of SSS effects is however done in an object's volume, not on its surface. Therefore, the final look of the SSS effect is determined by the shape of an object's volume, not its surface.

Objects created in 3ds Max appear smooth by default.

We can however see that they are really faceted by disabling the "smooth" option in object's properties.

2. Solutions

There are ways to improve the appearance of such faceted objects:

1. Subdivide the geometry
Subdividing the geometry has two effects which are important here:
  • it makes faces smaller
  • it reduces the differences between face angles
Usually the objects can be subdivided to such a degree that the faceting will not be noticeable:

Segments: 32

Segments: 64

Segments: 128

The same can be achieved using modifiers, for example TurboSmooth:

Object subdivided using the TurboSmooth modifier.

2. Change the SSS material settings
Changing absorption distance allows rays to travel deeper into the object's volume, which makes it appear softer, and reduces the faceting. This however does affect the appearance of the material, and thus cannot be used in all cases:

Absorption distance: 0,1m

Absorption distance: 0,2m

Absorption distance: 1m

For a general SSS guide, see:

How to use subsurface scattering?