The VRay2SidedMtl material is a utility material provided with the V-Ray renderer. The material allows seeing the light on the backside of the objects. Use this material to simulate thin translucent surfaces like paper, cloth curtains, tree leaves etc. For further info see the Example sections.
Parameters
Front material - this is the material which is going to be used for front-side faces as defined by the object normals.
Back material - this is the material V-Ray will use for back side faces as defined by their normals.
Use back material checkbox - when this is off, V-Ray will consider both sides assigned with the front material. When this is on, you can assign a different material from the front one. For further info see the Example sections.
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, 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 0.0 the more of the material facing the camera is going be seen. When it is closer to 1.0, the more of the back material is seen.
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.
Notes
This material will give best results when assigned to singleside objects (non-shelled) objects like planes, extruded splines etc. Otherwise it can lead to extremely longer rendertimes.