In Cycles the Layer Weight node has an output called Facing.
In Blender Internal the Geometry node has an output called Front/Back.
Do these perform the same function and just have different names, or are they doing something different?
Thanks
Do these perform the same function and just have different names, or are they doing something different?
No, they don't. They perform something different:
Facing output from Cycles Layer Weight node gives angle of incidence. You can read about this node and how it compares to the Fresnel node here: Relation between Fresnel IOR and Layerweight blend?
You can make it from scratch in Blender Internal node material like this:
Front/Back output from BI Geometry node is the same as Backfacing output from Cycles Geometry node and gives a binary true/false (1/0) if a face is oriented to the camera with it's normal or not.
The Cycles Layer weight node is used to emulate Dielectric materials, useful for example for layering diffuse and glossy shaders to create a plastic material with Fresnel effect. It's used as a factor mask between 2 shaders when they are combined with the "Mix shader" node.
Whereas Geometry node for the blender internal is used for specifying how light reflects off the surface. This node is used to change a material’s Normal response to lighting conditions. Use this node to feed the Normal vector input on the Material node.
Answer So no they are not the same thing.
The weight node affects how 2 shader composite on top of one another. The Geometry node in Blender Internal uses the material's setting to overwrite your mesh's normals.
However there is a Geometry node that is in Cycles that is similar to the Geometry node in Blender internal. I have created a small blend file for your reference.
Also check this video out ... it shows how the Cycles geometry node is used. https://www.youtube.com/watch?v=lOSoGvw97XI