Cool. Glad you found it. 

However, specific to your request about fading from the interior to the exterior, here's a sample I just put together using Shoestring Shader's Proximity function. At the center of the tree I've placed a sphere but turned it's visibility off. The shader will still "see" it and invoke the function. The other little gradient tricks from the other thread can still be used to augment the variations though!

If you expand the image you can see how I set up the Shader Tree.

Mark