Subsurface Scattering

Create a glossy material where subsurface scattering is also supported.

Subsurface scattering materials involve the interaction of surface reflectance/transmittance along with scattering through participating media.

When scatter density is much higher than absorption density the material will take longer to render.

Main Parameters

Surface Color
To define the color, choose from the following options:
  • Select a color.
  • Select an image. The image overrides the color.
  • To blend the color with the image, click the plus symbol (+). You can tell if the blend option is turned on by looking at the image preview.

To define the shade, enter a value of 0-100, where 100 is the true color and 0 is black.



Figure 1. Satin Black Plastic from the Material Library
Index of Refraction (N)
Define the reflectivity of the surface. Higher values correspond to more intense reflections.

If you selected a preset, this value is predefined. If you selected a custom preset, look up the index of refraction online.

Absorption Color
Define which colors of the spectrum are absorbed (thus not visible) by uploading an image or picking a plain color. The remaining colors of the spectrum are reflected (thus visible).
Absorption (1/m)
Use this feature to adjust the intensity of the Absorption Color.


Figure 2. Opal Glass Simulated Using the Default Values of 100% for Translucency and 0 for Absorption
Scatter Color
Scatter Color defines the scattering color—this is the color that bounced particles (in the medium) have. The sum of absorption and scatter color (multiplied by their corresponding densities) defines the extinction coefficient of a medium which is used to calculate the total absorption at a distance. The scatter color may be applied numerous times for particles that bounce inside the medium (especially for highly scattering medium) and so, it is also recommended here to avoid highly saturated colors.
Scattering
With this parameter you can change the scatter density and color for a Subsurface Scattering material. Note that the higher the scattering, the more time it will take to render the material. The scatter density can take any positive or zero value and it is in 1/m units. Note that the scatter color is used both for defining the in-scattering and out-scattering light interaction.
Asymmetry
This parameter controls the asymmetry coefficient of subsurface scattering medium, assumed to follow the Henyey-Greenstein phase function. This parameter takes values between -1 and +1, with -1 corresponding to perfect back scattering media, +1 to perfect front scattering media and 0 to isotropic media.
Roughness
Roughness adds texture to the material at a microscopic level. When you modify the roughness, the surface texture still looks the same; however, tiny changes invisible to the naked eye have occurred, affecting reflectivity.


To add a roughness map, upload an image.

0 can produce a perfect mirror reflection.

Lower values produce crisper and brighter reflections.

Higher values produce blurrier, dimmer reflections. Increasing the roughness spreads and distributes reflections over the surface and creates a more matte surface.

At values approaching 100, light becomes so scattered that reflections are barely visible, if at all.

Bump
Bump adds texture to the material at a macroscopic level. Because it visibly affects the surface texture, Bump is useful for simulating irregular surfaces.
A bump map gives the illusion of texture without physically distorting the geometry, minimizing rendering time. The grayscale map tells Inspire Studio how to change the surface normals as if the surface had been displaced; the modified normals are used in lighting calculations. A bump map looks like the inverse of what you might expect: black represents the highest extreme and white represents the flattest extreme, while shades of gray represent grades in between.


No Bump (default): Do not use a bump map.

Use Surface Color for Bump: Reuse the image used for your color map and apply it as the bump map. You can make the bumps look taller or flatter by adjusting the bump effect (0 to 100); higher values make the texture look more pronounced, smaller values make the texture look more subtle.

Custom Bump: Upload an image. You can make the bumps look taller or flatter by adjusting the bump effect (0 to 100); higher values make the texture look more pronounced, smaller values make the texture look more subtle.

Normal Map OpenGL: Achieve more detailed texture effects when you have uploaded a RGB color image. While standard bump mapping uses grayscale values to describe the surface's hills and valleys in terms of height, normal mapping translates red, green, and blue values to x, y, and z coordinates, creating texture in terms of angles up the hill or down the valley.

Normal Map DirectX: Achieve more detailed texture effects when you have uploaded a RGB color image. While standard bump mapping uses grayscale values to describe the surface's hills and valleys in terms of height, normal mapping translates red, green, and blue values to x, y, and z coordinates, creating texture in terms of angles up the hill or down the valley.

Note: Roughness and Reflectivity are interdependent properties; smoother surfaces produce crisper reflections, while rougher surfaces produce blurrier reflections. For example, set roughness to 0 and reflectivity to 100 to produce a perfect mirror reflection. To make the reflection blurrier, increase the roughness.

Advanced Parameters

Anisotropy
Stretch and blur highlights. Anisotropic reflections are like regular reflections, except they are stretched and blurred against the grain of the material. They are often used to simulate finely brushed metals.
Rotation
Enter a value from 0 to 360 to rotate the stretched highlights. Rotation is only applicable if Anisotropy has been selected.
Micro Roughness
Adjust the sharpness of reflections, as the viewing distance goes from close to far. When you look at a surface that is uniformly rough, areas that are closer appear rougher (because you can see them more clearly) while areas that are farther away appear smoother (because you can't seem them as clearly). As a result, nearby reflections look blurrier while faraway reflections look crisper.

Height (μm): Adjust the average height of the bumps on the surface. Higher values correspond to blurrier reflections overall.

Width (μm): Adjust the average width of the bumps on the surface. Higher values correspond to blurrier reflections overall.
Figure 3. Micro Roughness Disabled
Figure 4. Micro Roughness Enabled with a Width of 10 μm and Height of 0.1 μm
Displacement
Bump allows you to render detailed textures relatively quickly; however, because you are only changing the surface normals and not the surface itself, silhouettes and shadows might not be rendered realistically. This condition is particularly true for larger texture effects. If you need to give surfaces a greater sense of depth and detail, showing self-occlusion, self-shadowing, and silhouettes, use Displacement. Like bump maps, displacement maps are grayscale; black equals zero displacement and white equals maximum displacement (a value you define using the Height parameter below).

This feature is not currently available in GPU+CPU mode.

The default number of samples is 500.

Subdivision: Modify the object's number of subdivisions before displacement occurs. Higher values produce more accurate results.
Figure 5. Subdivision: 2
Figure 6. Subdivisions: 6

Texture: Upload a texture map. Colored images will be mapped as grayscale.

Height: Set the maximum distance displaced. For displacement to appear, values must be greater than zero; the default is 2 cm.
Figure 7. Height: 0.5cm
Figure 8. Height: 25cm
Center: Invert displacement. This feature is useful for positioning objects along a ground plane. For example, adding a displacement map to a carpet may make it look like it's floating. Reducing your center will bring it back down to the floor. Adding a displacement map to a floor may result in objects intersecting with the floor. In this case, you could increase the center to avoid intersection.
Figure 9. Center: 1cm
Figure 10. Center: 0.1cm
Normal Smoothing: Enabled by default, to render smoothly (continuous shading). Disable to render in a faceted way, which is useful for rendering very sharp, detailed displacements such as sharp corners.
Figure 11. Normal Smoothing Disabled
Figure 12. Normal Smoothing On
Tight Bounds: Enabled by default. This feature lets Inspire Studio compute more precise bounding volumes for the displaced surface, leading to slightly better rendering times. Since this feature is performance-based, check your engine settings to enable your fastest processors.
Figure 13. Tight Bounds Disabled
Figure 14. Tight Bounds Enabled
Clipping
Make areas of the material transparent, using a grayscale texture map where black equals completely transparent and white equals completely opaque. This feature is useful for quickly creating perforated materials like a mesh, since you can skip modeling the holes by hand.

Texture: Upload a texture map. Colored images will be mapped as grayscale.

Threshold (%): Change how the texture map is interpreted. The default is 50, where 50% gray is interpreted as 50% transparent. To make a greater area of the texture transparent; increase the threshold; to make a greater area of the texture opaque, decrease the threshold. At 100, the entire texture is transparent; at 0, the entire texture is opaque.

Soft: Soften the contrast between completely transparent and completely opaque.