The Fresnel effect
The Fresnel option available in shader parameters is used to modify the reflection intensity, based on the viewing angle, to simulate a metallic behavior. After 3D rendering, altering this property requires rerendering. Blender provides an alternate method to build and modify the Fresnel effect in compositing, using the Normal node.
The following screenshot illustrates the Fresnel workflow. In this procedure, the dot output of a Normal node is connected to the Map Range node and the To Min / To Max values are tweaked to obtain a black-and-white mask map, as shown in the screenshot. A Math node is connected to this mask input to clamp information to the 0-1 range.
The 3D-combined render output is rebuilt using the diffuse, specular, and reflection passes from the 3D render. While rebuilding, the mask created using the Normal node should be applied as a mask to the factor input of the reflection Add node. This results in applying reflection only to the white areas of the mask...
