Each BSDF node now has a Normal input, which can be used to set a custom normal
for the BSDF, for example if you want to have only bump on one of the layers in
a multilayer material.
The Bump node can be used to generate a normal from a scalar value, the same as
what happens when you connect a scalar value to the displacement output.
Documentation has been updated with the latest changes:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes
Patch by Agustin Benavidez, some implementation tweaks by me.
undesired dark rings, and give more accurate lighting when the light is
behind the object. As a bonus, the code is simpler & faster.
Patch by Yasuhiro Fujii, detailed explanation here:
http://mimosa-pudica.net/improved-oren-nayar.html