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Subsurface Scattering

Subsurface Scattering allows light to penetrate an object and bounce through it, as though the object were made of many translucent layers. This technique is commonly used to simulate skin.

  • Subsurface Scattering
  • Color
  • Refraction
  • Scale
  • Group
You can turn Subsurface Scattering on or off using a toggle button.
Figure A
Figure A
Figure B
Figure B

Figure A does not use Subsurface Scattering, but Figure B does. Diffuse Value was set to 0% in Figure B to better display the effect.

Subsurface Scattering is a time-consuming effect to render, but is a popular technique used by professionals to simulate materials like skin, milk and jade.

Subsurface Color lets you change the color of the light reflected by the inside of the object.
Figure A
Figure A
Figure B
Figure B

For instance, a person's skin might use a pink or an orange.

Subsurface Refraction lets you adjust how much light bends when it enters the object.
Figure A
Figure A
Figure B
Figure B

The higher the refraction, the more the light is bent. Skin typically uses a value between 1.4 and 1.5.

The effects of Subsurface Scattering will change depending on the size of the object.
Figure A
Figure A
Figure B
Figure B

You can use the Subsurface Scale property to adjust how big the Subsurface Scattering calculations think that the object is, without changing the size of the object in the scene.

The higher that you set Subsurface Scale, the smaller the object is considered to be, and light will more easily travel through the object as a result.

Use the Subsurface Group property to change which materials are considered to be part of the same surface.
Figure A
Figure A
Figure B
Figure B

Note: pwSurface now auto-groups surfaces when Subsurface Group is set to 0. You can adjust this property if desired, but under most circumstances, it is not necessary to do so.

In the example images above, two different cubes are shown side by side. In Figure A, the green cube is in Subsurface Group 0, and the pink cube is in group 1, so light doesn't spread between the two. In Figure B, the two cubes are in the same Subsurface Group, and, not only does light travel through the inside of one cube to another, but all of the Subsurface Scattering properties are now shared.

This is something that you need to watch out for when using Subsurface Scattering. Not only do surfaces in the same Subsurface Group share light, but they also share color, refraction and scale.

When using a human figure, you'll want to be sure that the skin, lips, nostrils and nipples are all in the same Subsurface Group. When using multiple figures, you'll want to be sure that no two figures share the same group.