Render solidify backfaces in cycles? so i was following the first steps in this tutorial: https://www.youtube.com/watch?v=D4T1cDJryOI

Basically you use a solidify modifier to create an outline around your mesh, however it is only working on the viewport when you have cull backfaces checked on display.

 but it does not work in the render, it stills render those backfaces.
I've tried using the node editor an the geometry backfacing utility along with a mixed shader.
I think it's because your object is closed (so it's dark inside).

And it looks like IkariShinji gives the solution in blenderartists.org: "Making the backfacing faces transparent for the camera doesn’t automatically make them invisible to shadow rays."

So here is the kind of node organization you need to have to make your object transparent again, please tell me if it works: