Prepass rate - SSS Layer accelerates the calculation of multiple scattering by precomputing the lighting at different points on the surface of the object and storing them in a structure called an illumination map, which is similar to the irradiance map used to approximate global illumination, and uses the same prepass mechanism built into VRAYforC4D that is also used for e.g. interpolated glossy reflections/refractions. This parameter determines the resolution at which surface lighting is computed during the prepass phase. A value of 0 means that the prepass will be at the final image resolution; a value of -1 means half the image resolution, and so on. For high quality renders it is recommended to set this to 0 or higher, as lower values may cause artifacts or flickering in animations. If the chosen prepass rate is not sufficient to approximate the multiple scattering effect adequately, SSS Layer will replace it with a simple diffuse term. This can happen, for example, for objects that are very far away from the camera, or if the subsurface scattering effect is very small. This simplification is controlled by the Prepass blur parameter.

Scale - additionally scales the subsurface scattering radius. Normally, SSS Layer will take the scene units into account when calculating the subsurface scattering effect. However, if the scene was not modelled to scale, this parameter can be used to adjust the effect. It can also be used to modify the effect of the presets, which reset the Scatter radius parameter when loaded, but leave the Scale parameter unchanged.

IOR - the index of refraction for the material. Most water-based materials like skin have IOR of about 1.3.

Refraction Depth - this determines the depth of refraction rays when the Single scatter parameter is set to Raytraced (refractive) mode.

Overall color - controls the overall coloration for the material. This color serves as a filter for both the diffuse and the sub-surface component.

Texture Map - here an image texture or shader can be defined.

Sub Surface Color - the general color for the sub-surface portion of the material.

Texture Map - here an image texture or shader can be defined.

Scatter Color - the internal scattering color for the material. Brighter colors cause the material to scatter more light and to appear more translucent; darker colors cause the material to look more diffuse-like.

Texture Map - here an image texture or shader can be defined.

Scatter Radius - controls the amount of light scattering in the material. Smaller values cause the material to scatter less light and to appear more diffuse-like; higher values make the material more translucent. Note that this value is specified always in centimeters (cm); the material will automatically take care to convert it into scene units based on the currently selected system units.

Texture Map - here an image texture or shader can be defined.

Phase function - a value between -1.0 and 1.0 that determines the general way light scatters inside the material. Its effect can be somewhat likened to the difference between diffuse and glossy reflections from a surface, however the phase function controls the reflection and transmittance of a volume. A value of 0.0 means that light scatters uniformly in all directions (isotropic scattering); positive values mean that light scatters predominantly forward in the same direction as it comes from; negative values mean that light scatters mostly backward. Most water-based materials (e.g. skin, milk) exhibit strong forward scattering, while hard materials like marble exhibit backward scattering. This parameter affects most strongly the single scattering component of the material. Positive values reduce the visible effect of single scattering component, while negative values make the single scattering component generally more prominent.

Single scatter - controls how the single scattering component is calculated:

• None - no single scattering component is calculated.
• Simple - the single scattering component is approximated from the surface lighting. This option is useful for relatively opaque materials like skin, where light penetration is normally limited.
• Raytraced (solid) - the single scattering component is accurately calculated by sampling the volume inside the object. Only the volume is raytraced; no refraction rays on the other side of the object are traced. This is useful for highly translucent materials like marble or milk, which at the same time are relatively opaque.
• Raytraced (refractive) - similar to the Raytraced (solid) mode, but in addition refraction rays are traced. This option is useful for transparent materials like water or glass. In this mode, the material will also produce transparent shadows.

Single Scatter subdivs - determines the number of samples to make when evaluating the single scattering component when the Single scatter mode is set to Raytraced (solid) or Raytraced (refractive).

Front Lighting - enables the multiple scattering component for light that falls on the same side of the object as the camera.

Back Lighting - enables the multiple scattering component for light that falls on the opposite side of the object as the camera. If the material is relatively opaque, turning this off will speed up the rendering.

GI Scatter - controls whether the material will accurately scatter global illumination. When off, the global illumination is calculated using a simple diffuse approximation on top of the sub-surface scattering. When on, the global illumination is included as part of the surface illumination map for multiple scattering. This is more accurate, especially for highly translucent materials, but may slow down the rendering quite a bit.

Prepass LOD - XXXXXXX

Prepass Blur - controls if the material will use a simplified diffuse version of the multiple scattering when the prepass rate for the direct lighting map is too low to adequately approximate it. A value of 0.0 will cause the material to always use the illumination map. However, for objects that are far away from the camera, this may lead to artifacts or flickering in animations. Larger values control the minimum required samples from the illumination map in order to use it for approximating multiple scattering.

Map Preview Size here you’ll find entries from 64x64 (16 KB) to 4096x4096 (64 MB). The value controls the internal resolution of the map — the higher you set this value, the more detailed the map will be in the viewport. The value has no effect on the rendered result.Proceed with caution when increasing the Map Preview Size. Higher settings require more RAM and increase the filesize of the CINEMA 4D scene. OpenGL is also affected because the map previews must be loaded into the graphics card’s memory.