V-Ray Two Sided Material parameters
Search Keywords: 2Sided, backlight, VRay2SidedMtl
The VRay2Sided material is a utility material provided with the V-Ray renderer. The material allows seeing the light on the backside of objects. Use this material to simulate thin translucent surfaces like paper, cloth curtains, tree leaves etc.
Front - this is the material which is going to be used for front-side faces as defined by the object normals. You can either specify a color or connect a material here.
Back material - this is the material V-Ray will use for back side faces as defined by their normals.You can either specify a color or connect a material here.
Translucency - this determines which side (front or back) relative to the camera is more visible in the rendering process. By default this value is 0.5 gray, which means that both the side facing the camera, and the one facing away from it, will be visible to the same degree. When this parameter is closer to black (0.0) the more of the material facing the camera is going to be seen. When it is closer to white (1.0), the more of the back material is seen. This parameter can be textured.
Force single-sided sub-materials - when is is on (the default), the sub-materials will render as one-sided materials. Turning this option off is not recommended.
The Material ID group is described here