The Sheen rollout is part of the VRayMtl parameters.
Parameters
The Sheen layer can be used for creation of cloth material, such as satin. You can find additional information on how to use them at Coat and Sheen Layers.
Sheen Color – Specifies the color.
Amount – Specifies how much the sheen layer overlays the diffuse color. The higher the amount, the more of the sheen color you get. See the Sheen Amount example below for more information.
Sheen Glossiness – Controls the sharpness of reflections. A value of 1.0 means all of the light reaches the diffuse color, and when the value is smaller, the cloth material looks glossier. See the Sheen Glossiness parameter below for more information.
Example: Sheen Amount
This example shows how changing the amount of the sheen layer affects the material. Glossiness is set to its default value - 0.8.
Example: Sheen Glossiness
This example shows how changing the glossiness parameter of the sheen layer affects the material. The Amount is set to its default value of 1
Amount = 0.1
Amount = 0.25
Amount = 0.5
Amount = 0.75
Amount = 1
Glossiness = 0.1
Glossiness = 0.3
Glossiness = 0.6
Glossiness = 0.8
Glossiness = 0.9