How to make the light emission invisible?

Question

I was experimenting with a scene with an object that is unwrapped so that every polygon has the same texture so that I can use it as a wireframe. The object is sitting on a plane. I tried this node setup, but it is not as I expected, because for some reason the main material casts light.

Here is what I want to achieve: the wireframe should be a light source that doesn't cast light. By the way, there is no other light source in the scene that is lighting the object.

However, it works this way:

However, in this way only the wireframe of the object is visible. How can I make the wireframe only to be a light source and not to cast any light?

If I confused anybody, then this is what I mean: http://cgcookie.com/blender/2011/10/20/blender-tip-creating-invisible-lights-in-cycles/

Answer 1

You can use a Light path node to mix shaders based on the properties of the incoming ray.

For example, this node setup mixes Base material and Line material based on Line texture, then mixes that with Base material based on the kind of incoming ray; rays coming directly from the camera will see the mix of Base and Line, but other rays will "see" only Base.

So shadows and indirect lighting etc. will be cast as if Base shader was connected straight to the material output.