Looking for a hard fast way of making an object see through. This is stupidly easy in blender render, but in cycles render, messing with alpha does nothing i can perceive .
It can be done simple with a mix of translucent and transparent shader, but it becomes tricky when you want to use Fresnel with it. In case you use Fresnel you need to flip the IOR values at the backface. Here below a node setup with Fresnel and correction for it for the backside of the face:
And the result:
And Without the correction you get this:
The algorithms used by Cycles are fundamentally different than those used by BI, and this sort of thing is one of the side-effects.
I routinely handle this sort of thing using separate renders, even when using BI as I normally do, in order to give me flexibility and to save (render) time. The objects are rendered solid, into MultiLayer OpenEXR files with all sorts of layers turned on, then creatively composited. I can “tweak” the effect in the compositor much more quickly than I can by grinding through render after render after render trying to get it right.