anchor.diff:  
   It’s important to understand what we want as a specular reflection. We want it to be very neat when the roughness is low and very blurry when it’s high.
   
  -image::Roughness.png[Roughness,width="320",height="250",align="center"]
  +image::jme3/advanced/Roughness.png[Roughness,width="320",height="250",align="center"]
   As roughness increase the reflection gets more blurry.
   
   To do this, we have to resolve an integral called the *radiance integral.*
  
positive.code: 
  Here is what it looks like :
  
  image::integrateBrdf.png[integrateBrdf,width="320",height="250",align="center"]
  
  The nice part is that this map is constant for white light. It does not depends on the environment. So you can bake it once and for all then use it as an asset in your shaders.
  
  
negative.code: 
  A picture worth thousand words
  
  image::jme3/advanced/Cube_mapped_reflection_example.jpg[Cube_mapped_reflection_example,width="320",height="250",align="center"]
  from wikipedia : TopherTH at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html), GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons Here the reflected Ray is our reflection vector.
  
  Here the reflected Ray is our reflection vector.
  