This patch allows you to set a constant alpha for shadow and AO rays as well as allow you to override sampling settings per material (number of bounces and number of samples in branched path rendering). The alpha settings can be set for self-shadowing and self-ao only if necessary. The reason for these changes is to make fur (we have lots of furry characters) render faster and smoother and allow us to get the look we needed. By making it a constant setting in the materials, shader lookups were unnecessary and allowed a 4x speed improvement over a shader based solution.
Please find attached one of several patches for Blender and Cycles from Tangent Animation that were implemented for the production of Tangent’s latest film, Run Ozzy Run. It is our hope that these features will make it to the master branch of Blender as we have found that they are necessary for our production environment. You’ll find that these features either decrease render times or allow the director to more easily meet his vision on time and on budget. They are not intended to be accurate or physically correct.