How to generate Illuminated Marble (Onyx) on V-Ray for SketchUp
MasterTuts presents another useful sketchup video that shows how to generate Onix Marble material by applying the two sided V-Ray method for SketchUp.
The V-Ray Two-Sided Material, or Vray2SidedMat stands for a utility material that comes with v-ray renderer. It is possible to view the light on the backside of objects by applying this v-ray material. V-Ray Two-Sided Material is used to generate thin translucent objects like paper, lamp shades, cloth curtains, tree leaves etc.
The rendering process also becomes considerably faster with this v-ray material. Owing to the nature of this material, it is recommended to have single surfaces instead of a solid, because you would require for any refractive material.