Cycles / Ray Depth:

* Added a Ray Depth output to the Light Path node, which gives the user access to the current bounce.
This can be used to limit the maximum ray bounce on a per shader basis. Another use case is to restrict light influence with this, to have a lamp only contribute to the direct lighting. 

http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Nodes/More#Light_Path

This is part of my GSoC 2013 project. SVN merge of r58091 and r58772 from soc-2013-dingto.

intern/cycles/kernel/kernel_displace.h

@@ -57,7 +57,7 @@ __device void kernel_shader_evaluate(KernelGlobals *kg, __global uint4 *input, _
 #endif
 
 		/* setup shader data */
-		shader_setup_from_background(kg, &sd, &ray);
+		shader_setup_from_background(kg, &sd, &ray, 0);
 
 		/* evaluate */
 		int flag = 0; /* we can't know which type of BSDF this is for */