Using single-sided V-Ray materials for translucent effects

On the pbviz boards, Nicky asked how to acheive a translucent stained-glass look. V-Ray has a really simple way of doing this:

By using a single-sided V-Ray material, light passes through very convincingly:

VRay Translucent Lighting

 Original post: http://www.pbviz.com/forum/Topic3299-9-1.aspx#bm3301