"baking" normal map through a camera?

I tried searching but couldn´t find anything on this. I need some help with setting up a material that allow me to extract a normalmap of an object using an orthographic camera (instead of using a flat plane and the “bake” function)? I´m already creating all the diffuse textures and masks that I want through a camera except for the normalmaps and I would save some time being able to ectract the normal data using the same camera.

I found an outline for how I can do it by adding three “blend” textures to a material (one for each axis), project/map them on the object using “normal” and restrict the output for each texture to one axis before I proceed with rendering the whole thing like any other object.

However I can´t seem to understand how to configure the “blends” and all the axis options?

Here is what I found and used as reference: http://www.blender.org/development/release-logs/blender-236/normal-maps/