Example 1: Presets

Example 2: Prepass rate

Example 3: Scale

Example 4: Scatter and sub-surface colors

Example 5: Scatter radius

Example 6: Phase function

Example 7: Single scatter mode

Example 8: Color changes inside the material

Example 1: Presets

Here are some examples of the same object rendered with different presets; data for most of the presets is obtained from the paper "A Practical Model for Subsurface Light Transport" by H. Jensen, S. Marschner, M. Levoy, and P. Hanrahan based on actual measurings of material properties.

 

No global illumination was used for these images, in order to better show the sub-surface scattering effect.

 

Skin (brown)
Skin (pink)
Skin (yellow)
Milk (skimmed)
Milk (whole)
         
Marble (white)
Ketchup
Cream
Potato
Spectralon

Example 2: Prepass rate

This example shows the effect of the Prepass rate parameter. To better show the effect, the Prepass blur parameter is set to 0.0 for these images, so that VRayFastSSS2 does not replace the sub-surface component with diffuse shading when there are not enough samples. Note how low values of the Prepass rate reduce render times but produce blocky artifacts in the image. Also note that more translucent objects can do with lower Prepass rate values, since the lighting is blurred anyways. In the examples below, when Scatter radius is 4.0 cm, the image looks fine even with Prepass rate of -1, whereas the at this rate, when Scatter radius is 1.0 cm, there are still visible artifacts.

 

Scatter radius is 1.0 cm
Scatter radius is 4.0 cm
Prepass rate is -3
Prepass rate is -1
Prepass rate is 0
Prepass rate is 1

Example 3: Scale

This example shows the effect of the Scale parameter. Note how larger values make the object appear more translucent. In its effect, this parameter does essentially the same thing as the Scatter radius parameter, but it can be adusted independently of the chosen preset. The images are rendered without GI to better show the sub-surface scattering. The Single scatter parameter was set to Raytraced (solid). The Marble (white) preset was used for all images.

 

Scale is 1.0
Scale is 10.0
Scale is 100.0

Example 4: Scatter and sub-surface colors

Note: the "happy buddha" model is from the Stanford scanning repository (http://graphics.stanford.edu/data/3Dscanrep/).

 

This example shows the effect of and the relation between the Scatter color and the Sub-surface color parameters. Note how changing the Sub-surface color changes the overall appearance of the material, whereas changing the Scatter color only modifies the internal scattering component.

 

In the first set of images, the Sub-surface color is kept to green, and the Scatter color changes.

Scatter color is red
Scatter color is green
Scatter color is blue

 

In the next set of images, the Sub-surface color changes, and the Scatter color is kept to green.

Sub-surface color is red
Sub-surface color is green
Sub-surface color is blue

Example 5: Scatter radius

This example shows the effect of the Scatter radius parameter. Note that the effect is the same as increasing the Scale parameter, but the difference is that the Scatter radius is modified directly by the different presets.

 

The set of images below is based on the Milk (skimmed) preset. The cube in the lower left corner has a side of 1 cm.

Scatter radius is 1.0 cm
Scatter radius is 2.0 cm
Scatter radius is 4.0 cm

Example 6: Phase function

This example shows the effect of the Phase function parameter. This parameter can be likened to the difference between diffuse reflection and glossy reflection on a surface, however it controls the reflectance and transmittance of a volume. Its effect is quite subtle, and mainly related to the single scattering component of the material.

 

The following set of images are illustrations of the phase function for several different values. The red arrow represents a ray of light going through the volume; the black arrows represent possible scattering directions for the ray.

Phase function is -0.5 (backward scattering)
Phase function is 0.0 (isotropic scattering)
Phase function is 0.5 (forward scattering)

 

The nex set of images demonstrates the actual effect of this parameter in a rendering:

Phase function is -0.9 (backward scattering - more light comes out)
Phase function is 0.0 (isotropic scattering)
Phase function is 0.9 (forward scattering - more light is lost inside the material)

 

The next set of images demonstrate the effect of the Phase function parameter when there is a light source inside the volume. The images are based on the Skin (pink) preset with large Scatter radius and Raytraced (refractive) mode for single scattering with IOR set to 1.0. Front lighting and Back lighting are disabled for these images; only single scattering is visible. Note the volumetric shadows cast by the light inside the volume.

Phase function is -0.9
Phase function is 0.0
Phase function is 0.9

Example 7: Single scatter mode

This example shows the effect of the Single scatter mode parameter.

 

For relatively opaque materials, the different Single scatter modes produce quite similar results (except for render times). In the following set of images, the Scatter radius is set to 0.5 cm.

Omni light
Dome light with HDR texture
Single scatter is set to Simple
Single scatter is set to Raytraced (solid)
Single scatter is set to Raytraced (refractive)

 

In the following set of images, the Scatter radius is set to 50.0 cm. In this case, the material is quite transparent, and the difference between the different Single scatter modes is apparent. Note also the transparent shadows with the Raytraced (refractive) mode.

Omni light
Dome light with HDR texture
  Single scatter is set to Simple Single scatter is set to Raytraced (solid) Single scatter is set to Raytraced (refractive)

 

In the following example, VRayFastSSS2 was used to create the appearance of mirky water. Notice how the Raytraced (refractive) mode allows you to see through the water surface.

Single scatter is set to Simple Single scatter is set to Raytraced (solid) Single scatter is set to Raytraced (refractive)

 

Example 8: Color changes inside the material

This example demonstrates how the apparent color of the material might change inside of objects. In the first set of images, the Scatter color is set to grey, while the Sub surface color changes between red, green and blue. Note how the part of the surface that is directly lit appears with the Sub surface color, while the portion of the object away from the light gradually blends into its opposite color. This is because the light colors specified by the Sub surface color parameter are scattered out of the material near the surface, and only the remaining light passes through. (To better demonstrate this effect, the Single scatter mode is set to Raytraced (solid) for all images in this example.)

 

The Sub surface color is red (RGB 218, 58, 58) and the Scatter color is grey The Sub surface color is green (RGB 58, 218, 58) and the Scatter color is grey The Sub surface color is blue (RGB 58, 58, 218) and the Scatter color is grey

 

This effect becomes less apparent if the colors are more saturated, as demonstrated in the following set of images:

The Sub surface color is red (RGB 218, 13, 13) and the Scatter color is grey The Sub surface color is green (RGB 13, 218, 13) and the Scatter color is grey The Sub surface color is blue (RGB 13, 13, 218) and the Scatter color is grey

 

 

If this effect is not desired, the Scatter color should be modified. In the set of images below, the Sub surface color is set as before, and in addition, the Scatter color is set to a more saturated version of the same color.

The Sub surface color is (RGB 218, 58, 58), and the Scatter color is (RGB 218, 13, 13) The Sub surface color is (RGB 58, 218, 58), and the Scatter color is (RGB 13, 218, 13) The Sub surface color is (RGB 58, 218, 58), and the Scatter color is (RGB 13, 218, 13)